I took my server to a neighbor and hooked it up to his router. Using Find My Device on a Chrome browser, it came right up. So this is a problem with my network.
The SonicTransporter shows in my router Devices list as 192.168.1.207
The Android tablet I use is 192.168.1.157
A computer savvy friend suggest I reset the router. This makes sense, since everything was working fine for over a year until it wasn’t.