Retires in process model not working on wm 7.1


I am facing problem while implementing retries in step “send Meassage” or send to external external in initiator model.
I have implemented timeout with a finite limit at process step “Wait for Ack” and then I am iterating back on step “Send Message” again for maximum retry count as 4, but once the step wait for ack is executing once even after the timeout limit step is not getting transitioned back to send message step.

I have set up step retry count as -1.
I am on 7.1.2.

Any help to this issue will be appreciated.