Can't install Apps outside of Windows Store (S Mode)

This issue can be caused through two different scenarios. The first possibility (more common) is that the computer you have is in Windows S-Mode. The second scenario is that the computer is set to only allow installations of Apps from the Microsoft Store. You will find solutions to both scenarios below. 

Windows is running in S-Mode

1. On your PC running Windows 10/11 in S mode, open Settings  > Update & Security  > Activation
2. In the Switch to Windows 10/11 Home or Switch to Windows 10/11 Pro section, select Go to the Store (If you also see an "Upgrade your edition of Windows" section, be careful not to click the "Go to the Store" link that appears there.)
3. On the Switch out of S mode (or similar) page that appears in the Microsoft Store, select the Get button. After you see a confirmation message on the page, you'll be able to install Apps from outside of the Microsoft Store
4. Microsoft's own instructions can be found here as well.

If you've determined that your computer is not running in S-Mode, but continues to pop up with a warning of how the application you're attempting to install is not from the Microsoft Store, please follow the steps below.

1. Click on the search option of the navigation bar in Windows (bottom of the screen). Type settings and open the settings app
2. On the left navigation menu, click Apps. Afterwards, click on Advanced app settings. 
3. The first option should show as Choose where to get Apps. If it is currently selected as The Microsoft Store only (Recommended), you will want to change it to another option. The safest choice would to to select Anywhere, but warn me before installing an app that's not from the Microsoft Store.
4. Once selected, close the settings application, and attempt to install the 3rd party program again.