My apologies, I posted this in the thread to the other mod that was causing me this issue, but not here ...
Everything is working fine now.
It seems the
mgc_cb_evo.php file would not upload when I uploaded all of the files/folders as a group; once I uploaded this file by itself it was good to go. Why this one file wouldn't upload when all the others did, I don't know. But all seems to be working now, so I don't care.
I'd done a bunch of testing, but I never considered uploading each file individually - bad habits and all that. Anyway, that was the simple fix to the issue.