After upgrade, I get the following error:
Call to a member function external_star_rating() on boolean
There's no function in Moodle called external_star_rating() so maybe
this problem is caused by a plugin or other additional code.
Enable debugging under Site administrator ▸ Development ▸ Debugging to show more details of the error:
Do you have any additional plugins installed (go to Site administration ▸ Plugins ▸ Plugins overview and click Additional plugins)? If so what are they and which version.
What version of Moodle did you upgrade from?