Trying to view the admin panel. Can't get past that point. It also returns the same error when trying to view the homepage (the /public that fossbilling redirects to off index).
When I grep "locale_get_display_region" in the prinsfrank directory, it returns it in vendor/prinsfrank/standards/src/Country/CountryAlpha2.php, so that library seems to be complete enough... I don't know how the file is called as a function though, other than in composers autoload_static.php... but this is all someone else's code (not mine), so I don't want to go poking around too deep and get lost. The odd thing is, is that it was working for a short time before the error popped up and stopped me dead. I wasn't in the process of entering any data in, or anything... just tried opening the admin page, and wham. Full size error.