1
What error do you see when you try to install software on your PC, please provide a screenshot of the error.
2
Open the Settings App, then go to System - About.
What edition of Windows 11 is indicated as installed, is that Home or Pro or is it indicated a Windows S mode version?
3
In the Settings App, go to Apps - Advanced App Settings.
On that window, at the top is a drop down menu to choose where you can install apps from, is that set to 'Anywhere'?