I have 4 industrial PC's (single socket PC's) so I bought a 4 CPU license for community support. At the moment I licensed 1 PC but the other 3 will not register. Has anyone else seen this issue and have a solution?
A 4 CPU subscription is for a single server with 4 sockets.
In your case it should have been 4x 1 CPU subscription.
Best would be to contact Proxmox Shop team: https://shop.proxmox.com/contact.php