What do I do next? (see image). I have looked and tried things I have found (although I haven't found many things), but haven't been able to get rid of this message and fix this when I start illustrator. I have just been using it in safe mode to get work done, but think it may be interfering with things now. I don't see any troubleshooting tips. Please help. Thanks.
Looks like the preferences might be corrupted.
WHen did you last restart the computer?
Did you already rebuild the preferences?
Thanks for your reply.
I have restarted the computer several times since first receiving this message.
I tried rebuilding the preferences, but may not fully understand how to do that.
Thank you for the link. I've read through and tried its process. I've tried the Option+Command+Shift (macOS) as I start Illustrator, (as written in the link you sent), several times, and that does not seem to work. It doesn't do anything.
Where it says
It appears that the version number is already correct - 21... Not sure what to do next...
Go to this location: <OSDisk>/Users/<username>/Library/Preferences/Adobe Illustrator <version number> (21 in your case)
Remove or rename that folder itself. Then relaunch Illustrator and check.