Package is not added after instantiating in Julia

Question

I received a project environment from a colleague which contains the Manifest.toml, Project.toml and script.jl files. I tried to install the dependency for this project, which is just the ArgParse package, by running:

julia --project=. -e 'using Pkg; Pkg.instantiate()'

Then, when I start a julia session and try to load this package I get the message that the package is in General registry and if I want to add it:

julia --project=.
julia> using ArgParse
 │ Package ArgParse not found, but a package named ArgParse is available from a registry. 
 │ Install package?
 │   (my-env) pkg> add ArgParse 
 └ (y/n/o) [y]: 

I thought that by running Pkg.instantiate() all dependencies would be added so that one could start using a project, rather than manually adding these dependencies. Am I missing anything? Thank you.