If you are not able to log in to your proxmox server and it just show the error “permission denied – invalid PVE ticket (401)”
You can try a few things:
Try using another browser to see if the problem goes away, if so you can clear the cookies and data of your browser.
If that doesn’t fix the issue, as a last resort you can remove the file “/etc/pve/authkey.pub”, this file usually is rotated once per day but when you remove it Proxmox will recreate a new one in it’s place, this method wasn’t tested on a cluster environment.