Why is Entity Framework 6.0 unable to connect to SQL Server LocalDB in some cases?

Question

We recently deployed a version of our software that leverages LocalDB. We're using Entity Framework 6.0, and configured EF6 to create the database if it doesn't exist. Our intent is to use SQL Server LocalDB in a production environment. We have had success in all of our testing, and initial deployment has shown promise as it has been deployed on at least 15 stations without issue in our production environment. Sql Server 2016 LocalDB needs to be installed for it to work. In all cases, it worked out of the gate, since the database didn't exist, EF properly created the DB and all is well.

However, there is another group in our organization that also uses our software, and they had a different experience. Four out of five of their stations they deployed it on experience this same issue. Here is the error message and trace log.

"System.InvalidOperationException: This operation requires a connection to the 'master' database. Unable to create a connection to the 'master' database because the original database connection has been opened and credentials have been removed from the connection string. Supply an unopened connection. ---> System.Data.SqlClient.SqlException: A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 56 - Unable to load the SQLUserInstance.dll from the location specified in the registry. Verify that the Local Database Runtime feature of SQL Server Express is properly installed.) ---> System.ComponentModel.Win32Exception: %1 is not a valid Win32 application --- End of inner exception stack trace --- at System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, UInt32 waitForMultipleObjectsTimeout, Boolean allowCreate, Boolean onlyOneCheckConnection, DbConnectionOptions userOptions, DbConnectionInternal& connection) at System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, TaskCompletionSource1 retry, DbConnectionOptions userOptions, DbConnectionInternal& connection) at System.Data.ProviderBase.DbConnectionFactory.TryGetConnection(DbConnection owningConnection, TaskCompletionSource1 retry, DbConnectionOptions userOptions, DbConnectionInternal oldConnection, DbConnectionInternal& connection) at System.Data.ProviderBase.DbConnectionInternal.TryOpenConnectionInternal(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource1 retry, DbConnectionOptions userOptions) at System.Data.ProviderBase.DbConnectionClosed.TryOpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource1 retry, DbConnectionOptions userOptions) at System.Data.SqlClient.SqlConnection.TryOpenInner(TaskCompletionSource1 retry) at System.Data.SqlClient.SqlConnection.TryOpen(TaskCompletionSource1 retry) at System.Data.SqlClient.SqlConnection.Open() at System.Data.Entity.Infrastructure.Interception.DbConnectionDispatcher.<>c.b__13_0(DbConnection t, DbConnectionInterceptionContext c) at System.Data.Entity.Infrastructure.Interception.InternalDispatcher1.Dispatch[TTarget,TInterceptionContext](TTarget target, Action2 operation, TInterceptionContext interceptionContext, Action3 executing, Action3 executed) at System.Data.Entity.Infrastructure.Interception.DbConnectionDispatcher.Open(DbConnection connection, DbInterceptionContext interceptionContext) at System.Data.Entity.SqlServer.SqlProviderServices.<>c__DisplayClass60_0.b__0() at System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.<>c__DisplayClass2_0.b__0() at System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.Execute[TResult](Func1 operation) at System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.Execute(Action operation) at System.Data.Entity.SqlServer.SqlProviderServices.UsingConnection(DbConnection sqlConnection, Action1 act) at System.Data.Entity.SqlServer.SqlProviderServices.UsingMasterConnection(DbConnection sqlConnection, Action1 act) --- End of inner exception stack trace --- at System.Data.Entity.SqlServer.SqlProviderServices.UsingMasterConnection(DbConnection sqlConnection, Action1 act) at System.Data.Entity.SqlServer.SqlProviderServices.CreateDatabaseFromScript(Nullable1 commandTimeout, DbConnection sqlConnection, String createDatabaseScript) at System.Data.Entity.SqlServer.SqlProviderServices.DbCreateDatabase(DbConnection connection, Nullable1 commandTimeout, StoreItemCollection storeItemCollection) at System.Data.Entity.Core.Common.DbProviderServices.CreateDatabase(DbConnection connection, Nullable1 commandTimeout, StoreItemCollection storeItemCollection) at System.Data.Entity.Core.Objects.ObjectContext.CreateDatabase() at System.Data.Entity.Migrations.Utilities.DatabaseCreator.Create(DbConnection connection) at System.Data.Entity.Migrations.DbMigrator.EnsureDatabaseExists(Action mustSucceedToKeepDatabase) at System.Data.Entity.Migrations.DbMigrator.Update(String targetMigration) at System.Data.Entity.Internal.DatabaseCreator.CreateDatabase(InternalContext internalContext, Func3 createMigrator, ObjectContext objectContext) at System.Data.Entity.Internal.InternalContext.CreateDatabase(ObjectContext objectContext, DatabaseExistenceState existenceState) at System.Data.Entity.Database.CreateIfNotExists() at ResultProcessing.ResultContextInitializer.InitializeDatabase(ResultContext context) at System.Data.Entity.Internal.InternalContext.<>c__DisplayClass66_01.<CreateInitializationAction>b__0() at System.Data.Entity.Internal.InternalContext.PerformInitializationAction(Action action) at System.Data.Entity.Internal.InternalContext.PerformDatabaseInitialization() at System.Data.Entity.Internal.LazyInternalContext.<>c.<InitializeDatabase>b__58_0(InternalContext c) at System.Data.Entity.Internal.RetryAction1.PerformAction(TInput input) at System.Data.Entity.Internal.LazyInternalContext.InitializeDatabaseAction(Action1 action) at System.Data.Entity.Internal.LazyInternalContext.InitializeDatabase() at System.Data.Entity.Internal.InternalContext.Initialize() at System.Data.Entity.Internal.InternalContext.GetEntitySetAndBaseTypeForType(Type entityType) at System.Data.Entity.Internal.Linq.InternalSet1.Initialize() at System.Data.Entity.Internal.Linq.InternalSet1.get_InternalContext() at System.Data.Entity.Internal.Linq.InternalSet1.ActOnSet(Action action, EntityState newState, Object entity, String methodName) at System.Data.Entity.Internal.Linq.InternalSet1.Add(Object entity) at System.Data.Entity.DbSet1.Add(TEntity entity) at ResultProcessing.Processor.StartSession(TestSession testSession, ResultProcessingParameters parameters)"

The database is never created, and the application fails.

Here is our connection string. I don't know if this is relevant, but its set with Integrated Security=false, with no credentials in the connection string.

add name="MyDatabase" connectionString="Data Source=(LocalDb)\MSSQLLocalDB;Integrated Security=false;Initial Catalog=MyDatabase;AttachDBFilename=C:\MyAbsolutePath\MyDatabase.mdf" providerName="System.Data.SqlClient"

We have tried uninstalling and reinstalling SQL Server 2016 Local DB, and same result. We have looked in the registry and the location of the SQLUserInstance.dll is correct and the .dll exists in that location. We have searched for what this error could mean "System.ComponentModel.Win32Exception: %1 is not a valid Win32 application", and nothing related to this issue was found.

UPDATE:

Using SQL Server Management Studio, I'm able to connect to the server instance (LocalDb)MSSQLLocalDB on PC's that work.

On the PC's that do not work, SSMS is not able to connect to this server instance and produces the exact same error message.

This at least rules out our software application and hints at having something to do with the PC.