Invalid CSRF token when client tries to log in

A client has just started getting an error when trying to log in to the panel on their live site - “Invalid CSRF token”:

I am seeing the same issue when I try to log in. I have tried deleting session storage after finding a similar post on here but that hasn’t resolved the issue.

If anyone has any thoughts that would be super

Do you use a page cache like Varnish or caching rules in the web server config (e.g. in .htaccess )?


Thanks for the quick reply. Found the issue - the disk was full on their hosting.