I'm running Musicbee Wifi app on a SONY ZX507 (an Android DAP), and I'd get this error:
Unable to retrieve statistics from GoneMad player. The unlocked version of GoneMad is required, otherwise the the GoneMad error log.
I do have unlocked version of GoneMad, and there's nothing recorded on GoneMad's error log.
Strangely though, if I restart the device and immediately run Wifi app, it would sync normally.
I play music on flight mode when I'm out in order to save battery, then come home to connect to Wifi before attempting a sync. Not sure if this has anything to do with the error though...
It's more likely that the problem is on DAP's side, but in case anyone else is having the same problem (I remember seeing one in this thread), try again after restarting your device.