Theme keeps reverting to default

This happens when you have a faulty theme. If you set the theme to default or the classic theme, you should find that it won’t change themes. Often times this can be fixed by changing your theme, or you may be missing some files which need to be re-uploaded. Might be worthwhile to completely remove that theme, re-download it, and re-upload it. Also, if you aren’t currently running the latest version of WordPress, try upgrading.

Thanks for the tip but this happens no matter what theme I choose. It seems to be theme independent.

Oh and I’m running the latest version of WordPress. I upgrade with each new release.

Read this:
https://www.ads-software.com/support/topic/77582?replies=23#post-570631

It also happens to folks who have not followed the proper installation instructions for WP_Mobile plugin.