The error is "404 Category not found". Sorry, I thought that was obvious.
Joomla updater did not work, and I tried it many times over the course of 3 days and a lot of hours. I'm not sure what additional information you're asking for regarding the migration. The site was migrated to J3.3.6 with a fresh install of Joomla and migrating content and settings, then reinstalling components, etc. Later, to eliminate the possibility, I did the J3.4 upgrade, which went without a problem. Same "404 Category not found" error on both J3.3.6 and J3.4, so that didn't affect it. I read through the upgrade log file "joomla_update.php" to determine that the J3.4 update had no issues.
JEvents 3.1.42 is installed and working without any issues. It's the upgrade (in place) that's failing. I'm not sure what your suggesting about saving the configuration, as I am still running 3.1.42.
Thanks for the quick reply and your time.