Memory issue with Photoshop Elements 16.0 purchased on Microsoft Store

Error: An integer between 50 and 8 is required | Elements | Windows 10

Microsoft is the vendor and should help you in this case.

It seems that if you ask them, they will help you roll back to the previous Windows 10 version. Microsoft created the problem in its late Windows 10 (1803) update. Your problem is that their Microsoft Store version is built differently from the Adobe one to comply with their own rules. The workaround shown above has been tested by users like you. They reported that the registry edit is not exactly possible because there is no pre-existing subfolders for each Adobe Elements version. They solved the problem by creating the missing folders, leaving them empty except for the Elements 16.0 line.

No official endorsement for that solution, but as far as I can see from the hundreds of posts about the issue, your worst case will be that your edit will not be successful.