when i go to but cover image and screen shots for my game when i but screen shots he type for my Error Access and when i but cover image he type There's An issue with the file you selected..

Have you tried saving the images in a different file format or with another piece of software?

Another possible cause might be that itch.io uses scripts from Google in some places. If you are blocking Google domains or scripts for reasons of privacy this would be a possible explanation for the troubles you're having.