Error trying to upgrade in the GUI "the action you were trying to perform failed due to a security check."

[plittlefield]

I have updated my Docker containers and restarted with compose, then tried to update to 8.4.0 in the GUI, but got this error ...

An error occurred.
We're sorry, but the action you were trying to perform failed due to a security check. This is a standard measure to ensure the safety and security of your account. Please try again, and if the issue persists, please contact our support team for further assistance.

... what have I missed?

Paully