Problem: You get this error in the Admin panel when logging in on performing operations
There are a few possible causes of the problem, all linked to the Session:
Try reloading your browser to get a fresh token
Try clearing your browser session cookies, Try logging out and back in.
Ensure you are running under SSL and a HTTPS URL if you have
session.secure: true set in Grav's
Check that PHP has the correct tmp path set up. This can be set in PHP directly, or by setting Grav's
session.path setting (it can also be set via Admin, in the System Configuration) Reported issue