I had this exact problem after our past two renewals. First, I would make sure that the Gateways showing the license warning for AB/AV can, in fact, connect to Check Point. The first time I encountered this, we had upgraded the GW's to R80 right after the renewal and the "phone home" behavior definitely changed after the upgrade. These GW's sat behind other Firewalls, so I had to write access rules explicitly allowing the traffic. If you look in your logs for traffic sourced from the Gateways and/or Gateway Cluster object, you should be able to spot those connections.
I would also make sure your Contract file is up to date. Once you know your contracts are good. Go to the command line of the GW and run "contract_util mgmt". This should force the Gateway to update its contract file with the one on the management server. Hopefully, one of these steps will help you.
The second time this happened, I went many rounds between TAC and Account Services and no one could find a problem with licenses or validation on our GWs. The issue was determined to be "cosmetic" and once we passed the previous expiration date, the Gateways' Licenses cleared out and started showing the correct expiration without any warnings. It was very strange and a little troublesome waiting to see if something was going to break, but it did exactly what CP said it would.
Worst case, you can generate an all-in-one eval license and put it on the Gateway if it doesn't clear. You may want to have one or two on hand in case you need to drop them on.
R80 CCSA / CCSE