Replaced speaker for the second time, still no sound.

Hi,

i had to replace the top speaker. Everything went well: opening the case, taking the boards out and replacing the speaker, puttings the parts back again. The new speaker was doing it's job. Then i tested some other phone functions, screen, sound, usb, wifi... before putting the back on. Unfortunately the camera did not passed my test(HTC One M7 camera not working, open back). So i turned the phone off and posted that problem here. On the next day i turned the phone on and then again no sound from the top speaker. So i ordered a new one. I received it today and installed it asap . Unfortunatelly the new speaker is not working either.

I don't know what else i can do.

Thanks.