Hy John,
So glad to hear this was resolved, though I’m really sorry to hear about the fatal in the first place.
It’s tough to tell exactly why the error happened, but there is a shared common library between The Events Calendar and Event Tickets and it’s possible–based on the error text you posted–that the common library was not fully updated in one or the other. I don’t think it had anything to do with your process here, but it appears something was not fully loaded during installation.
In either case, I am really happy to hear everything is back in working order!
Cheers,
Geoff