Hi Jeremy,
I don’t know exactly which version of Events Calendar Pro we were on previously. The plugin was purchased on March 29th 2018 and hadn’t been updated since that time. The Events Calendar was not updated prior to receiving this error, we were in the process of running updates when this error started showing.
Your link to roll back instructions talks about making changes in WP Admin, which we cannot access. Should I just delete the plugin through FTP?