Forum Discussion
I would check that you have the same Sync Group Name specified on each GTM and also you would need to run the gtm_add command from bash once from each GTM you are pulling into the GTM Mesh, to get them to swap certs and build the iQuery connections.
Sync Group: DNS > Settings > GSLB > Group Name
https://support.f5.com/csp/article/K13312
Checking the sync connection with iQuery from the bash prompt and checking in /var/gtm should give you an idea as to what the issue may be.
OK I was missing the device cert for 1 of the units under gslb -> servers -> server certs. For some reason on 1 unit, it automatically added Self + Peer. One the other unit it only added Self.
That fixed iquery, then I had not also configured a data center and servers under gslb -> servers -> server list. Everything seems to be working now.