Why is my IMO ringing only once?

[Noufalg]

why is my IMO ringing only once

In my new Galaxy S6, while using the app IMO , its ringing only a single bell for the incoming call, Give me a suggestion.?
version 5.1.1
Made in UAE

 

[Sahedul Islam Sahen]

you are now imo beta inestol and enjoy problem solpt