So like everyone else some of my UE4 project wouldn’t open so before finding out this was a common problem that had solutions, I uninstalled UE4 with the intention of a clean re-install instead of verifying it’s files, because verifying takes too long in my experience.
For anyone who comes across this issue in the future, I solved it by deleting everything in the Epic Games folder, and installing an older version of the Epic Launcher from here: