Virtual server discovery

Please check iQery communication is working OK as mentioned under "Troubleshooting iQuery connectivity" in the following article:

K13690: Troubleshooting BIG-IP DNS synchronization and iQuery connections (11.x - 13.x) https://support.f5.com/csp/article/K13690

GTM and LTm are running on same VCMP and no discovery is seen

Did you create a server object with vCMP IP address?

Are virtual servers on the default route domain? if no, did you enable Expose Route Domains?