To check your LU policy in SEPM go to,
Policies page
Select LiveUpdate
On the right side, select the applicable LU policy for whichever group these clients belong in.
Open it up and select Server Settings
On this tab, right in the middle is the Group Update Provider button, select it.
Your GUP settings are in here. Make sure it is still a valid GUP. You can also set the option to bypass the GUP after "x" amount of time and get updates directly from the SEPM.
You definitely need to validate these settings to make sure they are still relevant.