Hello candicefromindinanapolis,
Thank you for using Apple Support Communities!
I understand from your post that you are being prompted for your user account password after you sign into iCloud and you are unable to download anything from the App Store. I recommend testing the issue while your Mac is in safe mode and/or in a new user account. This will help determine the cause of the issue. The following articles have the steps you will need to test the issue in both safe mode and in a new user account:
Use safe mode to isolate issues with your Mac - Apple Support
How to test an issue in another user account on your Mac - Apple Support
Best Regards.