Courses not saving, previewing or publishing

I inherited several Storyline courses created 3-4 years ago. They work just fine on an LMS, but need updating. I am able to open them and edit them just fine. But I get error messages whenever I try to now save them, preview any page(s) or publish them.

I've made sure the files are on my desktop, and opened them from my desktop. I've uninstalled Storyline 360, reinstalled it, and rebooted my computer.

Still no luck.

Any other suggestions? Thanks!