I had a similar experience in testing my setup: whilst exploring the use of the PMC-Eight Config Mgr I switched to ‘Serial’ with no serial cable connected and that was the end of my testing: I could only restore communication with the mount once I connected using the cable that was at that time still in the post! (I used to be a Software Consultant so I am a compulsive ‘tester’!)
Maybe there is a means of switching it back to UDP without a cable? I don’t know. Good luck with it.
Roger, Atherstone, England, UK
Mount: ES iEXOS-100, Celestron NexStar SLT
OTA: Celestron 127/1500 Mak , Svbony 60mm Guide scope
Camera: Svbony Sv305, Sv205