ModX newbie. I've built a few Joomla and Wordpress sites in the past and a friend asked me to help her with a ModX site for which the original developer is long since gone.
The site is 1.0.6 Evo (AFAICT) and has stopped working. Googling the error, it seems likely the webhost has upgraded PHP, and even if it isn't that then a 5 year old piece of software is probably due for a refresh.
I followed the alternate instructions at
https://docs.modx.com/evolution/1.0/administration/upgrading and have a new (1.2.1) and old backup of the files as well as a copy of the database all stored locally.
I uploaded and renamed everything and suddenly had a 500 error on loading the page, the manager and the installer. Tried putting the assets, manager and index.php back as they were and everything was back (old site still broken, but not a 500 error). I could get to the installer page. Tried putting the new ones back one at a time and narrowed it down to the manager folder triggering the problem.
I copied the ht.access file from the old manager to the new one, but still no joy.
Any other ideas?