Sorry but are you talking about a slicer where you use your shin inside his arm? or are u just using one of your forearms inside his arm
It wasn't hurting enough.
If a bicep slicer is done just right, it's almost impossible to NOT tap. I've tried to suffer through them. I've been through a lot of very painful experiences in my life and think I have a high tolerance for pain. I had to tap.
The break also might not happen instantly. Mikey has told a story here about how he didn't tap to a slicer in competition, and then the next day back in the gym he went to post on that same arm and it snapped, because the slicer had made a hairline fracture.