Hi Bill,
In your post of 2019-09-30, under Tests Failed, the second item says: PHP sessions not working.
But ok, if the emails are going out and if your calendar is working, then apparently the PHP sessions ARE working.
The SQL error in your first post is a
General error: 2006 MySQL server has gone away
This is not a syntax error, it's caused because for whatever reason the MySQL server doesn't respond anymore. It's very hard to say why this happens. From the SQL query string I can see that this happened when retrieving data from the calendar database. Because this function has not changed since years and never caused problems, I'm almost sure the problem has nothing to do with the calendar. If this problem happens often, if possible, I would suggest to open a ticket with your provider and ask if they can have a look in the server logs to see if they can find out why the "General error: 2006 MySQL server has gone away" errors occurred.
Roel