Failed to load descriptor file

I just bought and downloaded Tower Unite from Steam for my son. It downloaded successfully but when I try to launch the game, it gave this error “Failed to load descriptor file ‘…/…/…/Tower/Tower.unproject’”. What should I do? Thanks.

Try following the steps at the link below.

https://support.steampowered.com/kb_article.php?ref=2037-QEUH-3335