Why are my Greek characters being inserted in the database as question marks(?) when using parameterized queries?

Question

DBMS = Intersystem Cache' Driver Version = 2018.1.2.309.5

The below is a sample of the code I'm using:

Dim strsql = "UPDATE TBLSTK SET ICDESC=? WHERE ITEMNO=27227" 

Using cmdsrv As New Odbc.OdbcCommand("", myConn)
    cmdsrv.CommandText = strsql
    cmdsrv.Parameters.Add("ICDESC", Odbc.OdbcType.NVarChar).Value = "2ΤΟ ΧΡΙΣΤ/ΚΟ ΔΕΝΤΡΟ ΤΟΥ κ.ΓΟΥΙΛΟΜΠΙ"
    cmdsrv.ExecuteNonQuery()
End Using

This is the result in the database: 2?? ???S?/?? ?????? ??? ?.G????????.

If, on the other hand, I use the below query to update the record, the data will be inserted correctly.

Dim strsql = "UPDATE TBLSTK SET ICDESC='2ΤΟ ΧΡΙΣΤ/ΚΟ ΔΕΝΤΡΟ ΤΟΥ κ.ΓΟΥΙΛΟΜΠΙ' WHERE ITEMNO=27227"

Using cmdsrv As New Odbc.OdbcCommand("", myConn)
    cmdsrv.CommandText = strsql
    cmdsrv.ExecuteNonQuery()
End Using

This is the result in the database:

2ΤΟ ΧΡΙΣΤ/ΚΟ ΔΕΝΤΡΟ ΤΟΥ κ.ΓΟΥΙΛΟΜΠΙ