Norton is not showing as being on all of my devices

When looking at "Your Devices" only my iPhone and iPad have the green tick - our 3 computers have a red cross on them.  Yet when I look at "Manage My Installs" all 5 devices are listed and appear to be ok.  Two of our computers are running on Windows 8, and one on Windows 10.  I'm worried that we aren't sufficiently protected despite the subscription end date being 1st May 2016.

Can anybody help me with this? I've looked through all help areas and nothing seems to cover my issue.

Cheers Debski