vCenter 6.5 says valid license will expire

Recently upgraded from 5.5 to 6.5 on about 40 hosts. We had our licenses upgraded, and all was working fine for 6 weeks.

I'm now getting an error message in vSphere for four of the hosts which are in the same subnet saying:

"Your host license expires in 10 days. The host will disconnect from vCenter Server when it's license expires."

I've double checked all the hosts to make sure that license isn't being used elsewhere. Have tried renaming the license and then removing and re-adding the host to vSphere, issue persists.

Any ideas? Here is the license the server is using:

and here is the license details:

Thanks in advance.