If you want to move your subscription key to a new server, for example because you have replaced your hardware or you re-installed, you have to reissue your key via the client portal.
- Go to https://shop.proxmox.com/clientarea.php?action=services
- Click on the subscription key you need to reissue
- There you can click on the button "Reissue License"
- Now upload the key to your server and click on "Check" in your subscription tab right after.
You can make a server change three times per key. If you need more server changes, you have to make a request via the contact form https://shop.proxmox.com/contact.php
If you have ordered your subscription via a Proxmox Partner, just contact them for help.