Sounds like it was pretty frustrating, Laura, but I'm glad to hear you got it sorted out with the help of our Support team.
I finally called support as I was losing so much work time trying to figure out on my own! We discovered: document would not save because of an "over set" text box. I just "upgraded" to CC membership so this is a new requirement even from CS6. You can no longer leave extra text not visible in text box. (maybe you can leave on paste-board while copy-fitting, not sure)
That's also why I could not create a PDF - yet the error msg there said something about "background tasks". Whew! I also had to dig to find number to call. But had excellent help from the call.
Another note: google Chrome would not "play well" with Adobe Share for diagnostic connecting, so we switched to Safari. (good reminder that browsers are finicky) Thanks for responding and hope this helps others...
What Adobe product or service are you getting this error?
Is it, for example, Adobe Acrobat as part of your Creative Cloud membership?