Hi there,
Eventually I just deleted the events plus plugin, and then updated the rest, and then installed the old events plus plugin, and then updated it.
The issue was the order in which you updated the plugins and woo commerce, which also needed updating!
The line in question says bomb the site, if the versions are incompatible.
It is the first time that I have had a plugin prevent me from actually logging on.
All resolved now, and fortunately did not take too much to do. But, not being able to login, meant that I could NOT use updraft plus backup!
Please test a bit more throughly next time.
Cheers.
Arwyn.