Help Speaker and Earpiece not working after connecting to Bluetooth Speaker :(

[Navin Das]

I've been using my Bluetooth Speaker using Oneplus 3 and other devices since months, but one day when I paused the song from my bluetooth speaker pause button and when disconnected my Oneplus 3. After this my Speaker and Earpiece stopped working.

I tried Hard Resetting but the problem still persist. For time being, I'm using an Application called SoundAbout, but this is temporary solution.
What should I do ?
please help me!