First try restarting your IDE and see if something happens. If not then Delete your python installation using revo uninstaller to ensure deep clean. Reinstall python using the official installer from their website. Make sure to use the default installation and add it to PATH. After that create a .venv in your project directory. If you already have one delete it. And reinstall all the packages in the venv. I have faced issues with pyside6 similar to yours where python can't find a package even though it's clearly installed. The only fix I have found is to delete the .venv folder and reinstall everything. It's apparently a common-ish thing with pyside6.

It's common sense to not use any SDK installed from the ms store. MS store is good for regular people using regular apps not Devs using dev tools. Btw, use pycharm for easier python coding. Pycharm CE is free.