I backed up my database files as well as the web files, set up a test server and ran the upgrade. However, I didn't think to create a test database for the purposes of testing it, and the upgrade process ran all the way, including any database updates. I ran into issues enabling the oauth2 plugin for our IMAP communication with our Exchange server. I believe I've carried out all the steps correctly, but can't get any tickets downloaded from Exchange - meanwhile, the live server is stuck attempting to upgrade (which I never initiated, being on a test server), and it's coming up with the message "The upgrader does NOT support upgrading from the current patch [83a22ba22b1a6a624fcb1da03882ac1b]!". I suspect this is related to the v1.6 system trying to communicate with the database, but I'm not sure. At the moment, I'm a bit stuck - I'm a bit nervous about restoring the database backup and breaking everything completely.
The system is running PHP8.0, and MySQL 5.6.
Any help will be appreciated.
Alan