Thanks Leon, unfortunately the update was made by a script in cpanel (softaculous) from my hosting provider
. I have no control over the update process. I ask them to restore a server
backup from 30 august, and get back to version 3.7.7. Everything was working fine.
I've tried another update yesterday to 3.9.1, and again I can't open any page from the administration block or links in tabs.
Only Notifications, Registration, Moodle services, Feedback settings and Advanced features are working. Users, Courses, Grades, etc... aren't working (expanding), and no link is shown.
I've noticed that when the mouse pointer is over the language menu and user menu, both links point to .../admin/search.php#, and when cliking the page scrolls up to the top, but no dropdown menus are shown.
Direct links in courses and classes are working fine, but most dropdown menus or tab links aren´t working.
From the browser console, the only error I get is this: