You don't hear anything

If you do not hear the IVR test while calling 32843 and you can see in the logs a message similar to:

 DataTranslator::attachChain [0x7fe8340052b0] 'mulaw' -> [0x7fe834006f60] 'gsm' failed

then the gsmcodec module has not loaded. In this case you should reinstall Yate and YateBTS after you made sure you have the libgsm1-dev installed.