3.2.1 Won't Arm

I have APM 3.2.1. I am a bit new, but have followed the wizard and read the forums to find help, but nothing seems to be there for my problem.
I have 3dr Power module installed.

Problem is, I can’t get my hex to arm. I tried disabling pre-arm checks. I have programed ESC’s directly and done all of th trouble shooting I could find on the forums.
I reinstalled, rewired. took everything apart and started over and still can’t get it to arm.
Not sure what else to do. Any suggestions.
I have spent 2 days trying to figure this out.

This might be an obvious suggestion, but have you tried arming while connected to the ground station software (ie: Mission Planner)?

Most often, the GS will tell you why the arming is failing.

I connected to ground station and did everything I could. Finally I started over again and used different battery and still didn;t work.
Eventually I gave up.
Then went to try it again the next day. Didn’t change anything and it suddenly worked…so frustrating that I spent two days on this and nwo I son’t know what the problem was and I am totallly nervous about the reliability.

Seems to be bench testing ok right now…I will have to put some props on and take her outside for a true test.