İ have the same issue Samsung Galaxy s7(exynos) and found out that if you disable DVC it will come out the headphones and with it on will come out the speakers...Been using Poweramp for about 2-3 months and just had this issue today for the first time.Dont know what caused this issue only thing i can think off is the update that i got for Avast antivirus,messenger,facebook,google drive,Google maps, istagram and Kuveyt turk app(Turkish bank app)