viber sound

[Android Question]

Hello

I have my mobile phone (huawei ascend G510) for 2 months and I never got a call on viber. I can hear the person I talk to, but the person can not hear me. I tried with several people, it does not work.
I was advised to uninstall viber and reinstall, but it still does not work. The people I talk to can not hear me at all. I put sound up, my internet connection is fine. I do not understand why it does not work.

Please help me. Thanks