I am at this moment playing music on Radio but the Now Playing page says "Nothing".  Steps that got me here:

** 2 Radios connected to 7.4 r28547.  Fw= 7622

1. I played music#1 on Radio A
2. I stopped the server
3. Music ran out on Radio A
4. I started server
5. Radio A never reconnected to server, neither did Radio B. (radio B was not playing music.)

6. I switched Radio A to a different 7.4 server, and then switched it back to the first server.  It connected immediately.
7. From the WebUI, I played music#2 to Radio A.  It began playing, but... the "Now Playing" screen displays "Nothing".  Further, the Radio goes into its screensaver after a bit, thinking that nothing is playing I suspect.

Diagnostics screen shows all is well, with one exception: it indicates that Radio A is still connected to the second 7.4 server.  But it's not.  I'm playing music from the first server and controlling it from the first server.