Connection Manager - Automated Failover

I am in the middle of stress tests against a HDR pair (Primary + Updateable). I took down the primary and waited for CM to start the automated failover; it didn't. CM said "Arbitrator detected majority of secondarys are still connected." Please note that I had already tested the automated failover feature in the past when the servers were still being built and it worked as expected. From the logs, it looked like CM kept checking the Secondary to be less active for a failover, but the endurance testing is 15+ hours and won't be slowing down anytime soon. Is there any workaround to take advantage of the automated failover feature during a heavy usage? Or will it always wait till the box is less occupied?