I use an h2o sim $10 bucks for LTE minute plan 90 days
https://www.h2owirelessnow.com/
That's what I am using. Both the sim cards work perfectly in my other two L3G for V2 Phantoms
It's the Jewish holidays in Israel this week and most people take off until Thursday.
After installation with the CAN BUS external cables and new Flytrex, I had a similar issue in that the 2 red lights would not go off and the Flytrex unit would not initialize on power up of the drone.
I began also getting an intermittent MC ERROR (and please restart the Phantom). After checking all of the connections and calling H2O wireless to be sure my SIM card was okay, I reinstalled the V1.4.0010 firmware. You first have to reinstall the V1.3.2 and then reinstall the V1.4.0010.
I unplugged the 4 pin connector to the Flytrex when I did both firmware updates.
After the reinstallation, both the Flytrex worked and the MC ERROR stopped.
Not sure what caused the glitch, but it was something to do with the installation which was cleared by the firmware reinstall. Hope that helps and let me know if it works for you!!
Actually, I did have to do that with my firmware updates already because of the fact that I wasn't planning on flying the P3 until the Flytrex arrived and was way behind in doing firmware updates. It would not allow me to install v1.4.0010 until I did the v1.3.2 update. Now when I try to do the v1.3.2 it says a newer one is already installed. Now if I try to do the v1.4.0010 again, it says an identical version is already installed and aborts. I will just be happy and return it for credit and use my Trackimo and hope I never have to use it. Found a nice mount for it that looks and mounts just like the Flytrex one. Better than having nothing which is what the Flytrex is right now. To say I'm disgusted is an understatement!
I'm not sure our symptoms are the same. My problem is only apparent with the sim card installed in the Flytrex. On power up I get brief blue, then red, then steady green with the sim card removed. With it installed I get the same brief blue, then red, then after awhile it goes blue again then red while never getting any green. It repeats that cycle over and over. Both my H2O sims work perfect in my other two L3G Phantom V2 versions. So I am confident they aren't the problem.
My P3P must have a curse on it because it has been problem after problem. The first one was DOA and had to be replaced. I can't imagine what would be happening to it if I was actually flying it much.
Thanks for your reply and I will give it another try but I doubt anything is going to change.
I'll give you a hoot back and let you know what happens.
UPDATED:
I did the firmware update again. Same result. Checked all the pins in all the connectors to be sure none were bent, all found to be OK. What I neglected to mention in my earlier reply is that after it tries to initialize with the sim card in; The final result is a flashing red led. Not steady. It gives one blink, short pause and then five blinks and repeats over and over. Must be a failure code. But I can't find out what it might be. It still seems to boot normally without a sim card in it.
That's it, I'm done with Flytrex. I just hope I can get my money back and not have to mess with any more chance of damaging my P3.