Zoiper close unexpectedly once open

Question

Hi,

The application close unexpectedly after perform the following steps:

1. Install Zoiper in iPhone with iOS 10.3.1 (first install)
   
2. Open Zoiper 
3. Setting: Audio Codec: GSM, Video Codec: VP8, Enable SRTP
4. Purchase the SRTP plugin in AppStore
5. Open Zoiper
6. Zoiper close unexpectedly

It seem the SRTP plugin is causing the problem, because, previously, I didn't setup the application and it can open without problem.

I tried uninstall and install the application, but the problem persist.

Any suggestion?

Thanks!

JC