Site is down - CalendarAdminKey does not exist
My hosting account is configured to use PHP 5.6.37. My htaccess file sets PHP5.6 Single php.ini as the default. I've confirmed this using the info.php file.
There is no version file to ref. The update file refs version 8.2.1_remote_updater which does exist in the updates dir. There is the recent 8.4.3 update dir in there as well. I also have a 7.5.13 update dir in there.
After the successful restore I didn't edit/delete anything. Cache is still full.
When I attempt to load the site I get the following error:
Class Concrete\Core\Permission\Key\CalendarAdminKey does not exist
I've looked through the forums at length and have not found anything re this. There is a concrete\src\Permission\Key\CalendarAdminKey, but a "core" dir does not exist.
The page that does load has the bar across the top of the area with the C5 icon in the left corner suggesting it's trying to load the admin interface.
I'd appreciate some suggestions as to how I should proceed.