I had this issue as well. I am not sure if we have the same issue, but mine was a router content filtering setting. I was blocking “computer and internet security” and “computer and internet info” categories.
Thanks. We already have nimbus.bitdefender.net whitelisted. If I login into one of the PCs that shows "Protected by an older version of antivirus software" in the portal, the LogMeIn AV client on one of these PCs shows that the client is updated. I can also manually trigger an update from the client just fine. So it seems like the portal is not displaying accurate information as the client itself shows no problems.