This morning we experienced some license issues on one of our customers pages. We utilize a multi site solution, and this message appeared in turns on one sites different languages. To clarify, one out of 5 sites showed the message in some or all (not sure) of its languages. I'm 100% sure the 5 site limit isn't violated :)
What are possible explanations? I explored the MultiSiteRestriction class and notice that it depends on MachineWideValidation. Is it possible that the machine wide validation had some faulty state?
I usually get it when I reuse the license on a "staging" site on the same server that I only use for a few minutes before a deploy. Might be worth checking in IIS if you have any developer that has added another new site that contains the license too?