Also check your fuses for that matter. Many people have found fuses not pushed in all the way.Sounds like you have a bad amp if you are only getting sounds from the center speaker. You should get sound from all the speakers regardless to the stereo/surround setting.
You can always try to do a master reset of the Sync system to see if that fixes the problem.
https://www.ford.com/support/how-tos/sync/sync-4/how-do-i-perform-a-master-reset-with-sync-4/
I tried it nothing happend.If you think your speakers aren't working, press and hold the next track buttons (1: on steering wheel, 2: on dash) and it should make all 16/18 speakers beep one at a time.
Everybody else is correct though, check the fuses, try a much better audio source, try restarting Sync 4. The Unleashed is very front center heavy even in surround unless you adjust the fader just behind the front seats.
Just double checking, you pressed and held these two buttons together and nothing happened? I'd try resetting the sync 4 and if that doesn't work you might need to try the dealer.I tried it nothing happend.
Spotify does if you pay for their service.Its my understanding that most of the speakers will not work with sat radio in surround mode. There is too much compression. Some say it will work better in stereo mode.
Personally, with the unleashed, You need to listen to HD content if you want the speakers to work. Amazon HD radio, Tribal for sure. I'm not sure it pandora or Spotify offer an HD service.
Thanks for the offer, I am in Miami, FL. I will take it to the dealerThe 18 speaker system powers the Rear doors speakers and front tweeters from the Audio Control Module and all the others powered by the DSP on the back wall behind the driver side rear seat. If only the center is playing that is strange.