You may boot from a prepared USB.
Once booted, set the management IP from the console, and then access the webGUI.
When shown, enter the valid product key, and reboot.
After reboot enter the webGUI, and enter your active/active key.
Then, you may restore the settings and configuration from MAINTENANCE-->Misc page in the webGUI. Reboot, and activate the product.
You should be able to join the cluster then.
then i have my clusters back and can i access my other single volume?
And why we must enter our key again and why is this not valid anymore when is start.
can we use a temporary trail key to enter the boot modus?
the key is held on the boot media, so maybe a problem with that.
You may request a trial key when booting from USB, but it will likely come as expired since the system is in use already. Using your regular key is not a problem.