My subscription page says that the Subscription status is "invalid: subscription information too old".
When I click the "Check" button, after a while the message "Connection error - Timeout." appears.
Where can I find more information what is going on?
Your suggestion, together with the support of the shop team, brought me on the right path.
Ping to shop.proxmox.com resulted in an IP6 address which indeed does not work on our LAN. We do not support IP6.
The support team confirmed:
with the change of our subscription-check introduced in October 2022, the code
does not fall back to IPv4 on setups that have IPv6 addresses configured,
but where the outbound connections on IPv6 does not work.