Hi there!
I just downloaded my project from the link in original post, I put it on my desktop and unzipped it.
Then I just ran the .uproject and it created intermediate and loaded fine.
I am using 4.11.0 release, launcher version, I wonder why its not working for you? very strange!
I am not sure what else to do, so I’ve created a Content folder and migrated the assets to this folder, ala marketplace submissions.
Can you access and merge this content into a project? You’d then need to add Main to viewport via level BP.
www.lightningfitness.org/misc/video/UMGButtonErrorContent.zip
Nice to hear from you Rudy!