All hosts are esxi 6.5, and all licenses are this type: "VMware vSphere 6 Enterprise Plus to vSphere 6 with Operations Management Enterprise Plus for 1 Processor"
I would also like to add that all the hosts have been licensed correctly. The error came overnight, without any obvious explanation. While we where investigating the problem. One host crashed because of an hardware error. It had to be removed, and now we get an insufficient license error when we try to add it back in, even if there should be two available CPU licenses.
Tom Torum