When playing music from phone to car through Bluetooth no sound or bass comes through, front is ok.

[HOMIEGQ]

Samsung 6 edge plus Bluetooth to Kenwood car stereo with amp- no sound or bass plays to the rear speakers, but plays to the front with stock bass speakers.

I know its possible, because it worked before. I dont know what changed (maybe an update?).
I dont know when or how long ago.
I have the settings on car stereo as A2DP or on a music setting (I forgot what it's called).
Any help or ideas whould be greatly appreciated. Thank you.