This is the exact issue I was experiencing. I had to have a few days break to work on something else.. and will be revisiting this over the next few days.
I was getting this error when trying to setup a remote router that connected to a controller that I setup a while ago.. I believe the problem was with the controller PKI.. that caused this error
To resolve, @TheLumberjack provided the following instructions.. I have not gotten around to doing this just yet.. because I am trying to triangulate the specific cause of the problem
What I understand is that there is some problem with the controller certificates. I should have more updates on this over the next few days. I was hesitant to just do this in case it caused other problems.
In contrast, what I did do in parallel.. to help with understanding the problem ... was to setup a new controller on a new machine using a fresh install. This seems to have worked..
Hence.. I believe the issue relates to the controller PKI.
Maybe.. try setting up a new controller on a new server. If this works.. then you know it's something related to the controller config..
Hopefully I can pin point the exact issue.. of which.. this a great opportunity to learn more about how the controller PKI is setup.
@TheLumberjack also provided some great insights in this post.. definitely work taking a read through.