Error 0 sounds like an unhandled exception without a descriptive error code.
Edit your configuration.php file and change the following lines (they might not be one after the other or in the order presented below):
public $debug = '1';
public $error_reporting = 'development';
What these lines do is the same as going into Global Configuration and setting Site Debug to Yes and Error Reporting to Development. You should get a much more descriptive error message which would at least point you towards the issue you have.
As for restoring the backup. Do remember that restoring a backup only overrides existing files and creates new ones. It does not delete any files which now exist on your site right now but did not exist at backup time. If the update you made added files which are also able to be autoloaded by the old version of the plugin that broke you'd indeed run into the same problem.
In this case first download any backup archives still stored on your site. Make three copies of them in different media / storage services e.g. one on your computer, one on a USB key and one on a NAS / file storage service (such as Dropbox, OneDrive, Google Drive...) / another computer. The idea is that you want to be really darned sure you don't lose your backups!
Then restore the backup again. This time delete all files and folders (or at least the administrator, modules, layouts, plugins and templates folders) and then use Kickstart to extract the backup archive.
Nicholas K. Dionysopoulos
Lead Developer and Director
🇬🇷Greek: native 🇬🇧English: excellent 🇫🇷French: basic • 🕐 My time zone is Europe / Athens
Please keep in mind my timezone and cultural differences when reading my replies. Thank you!
