What version of SSIS is your packages? What version of Visual Studio are you using? What extension did you install and what version is it?
SSIS is tied closely to the version of SQL and older packages won't work with newer SSIS extensions if they dropped support. Refer to the supported versions document.
Also be aware that SSDT is now broken up and partially supported in VS 2019/2022 and partially through extensions. SSIS packages can only be opened using the SQL Server Integration Services extension which must be installed separately. This extension is not yet supported by VS 2022 so you'll need to stick with VS 2019 if you're using it.