"Failed to load assets" when trying to open level

On this one project that I’ve been working on for ages, one level won’t load. Whenever I click on it shows the error “failed to load assets”. This level took hours to make and is key to the game. What do I do?

Oh and also nothing comes up in the message log…

The question by this user was answered in this thread:

That worked for a different error (with a physics actor), but not this one…

Can you put up a screenshot of the errors you’re getting? I’m a bit concerned that your files may be corrupt. Do you have source control or a backup of your project?