I've had trouble trying to get an Excel file to connect to this SSIS package so I've uninstalled and reinstalled VS2019, Integration Services, and Access Server 64bit a half dozen times.
This most recent time I opened the SSIS package I created that started this whole mess and I got an error that it was incompatible. Not sure how as I created it using the exact same packages!
Now it will not allow me to Edit Script on any Script Tasks, even new Script Tasks in a completely new file!
After some time on Google I found some older posts with similar issues where Miscrosoft Visual Studio Tools for XXXX didn't uninstall properly and wasn't registered properly upon reinstall.
I went into Add/Remove Programs found I had tools for 2017 and 2019. I clicked Modify on them, and select Repair. Upon repairing them both the scripts could then be edited again.