I got a read with my Purewrist PAY on that Verifone MX 915 terminal that was giving me trouble. The issue is that some of the terminals have a huge metal clamp holding them, and others have a proper armature screwed into the back center.
Armature
Clamp
I was able to get a read no problem on the unit on an armature by placing the implant horizontally against the black area above the LCD. I still haven’t been able to find the sweet spot on the ones with the clamp. I think the large body of metal is affecting the field shape