I have a MES30 and use an AMPs I use a lot. Let me give you some things I learned.
Stacking the pellets in the tray, don't worry about too much, if it jumped the ridge to the next line, its burning good but if you keep the line filled only about ¾ of the way up, it likes it better and uses less pellets. A more complete burn.
Humidity, I believed it in the beginning, not so much now. I live in the extreme gulf south. It was just me looking for an excuse. Sure if you spray ‘em with water or leave ‘em out in the rain, but in a ziplock bag its fine. I have bags that have never been re-zipped that work. Did I mention 100% humidity is not uncommon here?
Pellets, There are differences in the pellets density just like in the actual woods, naturally some burn better than others. Cherry and Apple come to mind as hard to start and keep burning. I usually mix them with more reliable burners.
Air flow, now here is a for real problem, you must have heat to get airflow. You must have good suction and discharge available. I have actually seen one guy who solved his problems by moving his smoker further out from where it was sitting.
A good blow torch is needed.
I had the problem that I thought you could light and forget it, I was actually trying each time to beat my previous lite time. LOL. But then I began thinking, it’s going to work smoking for hours upon hours, I can spend 10 mins. getting it started right? Then I quit having problems.
I have tried preheating the pellets to dry them before trying to light them, yes and no, I learned that if I work at it even just a little, it smokes fine without heating/drying. I do though keep the Ziploc bags of pellets in a large plastic sealable tub. It is Louisiana and it’s common to have 100 % humidity days, and it not raining...LOL
Here's what works for me. I fill my AMPS tray, I check the wind direction. I set the AMPS outside the smoker facing the breeze; I use the torch (I have a butane mini torch afraid my Oxy/acetylene will melt the tray). I get a load red glow about like a cigar end AND I set a few more pellets on top of the burn after its lit. I let it smoke/burn a couple a min. blow it out and concentrate a blow on the coals enough to re-ignite it to a flame, then blow it out again while the smoker is heating with the vent closed. I have a cut up aluminum pan protecting the AMPS from drips. When I insert the AMPS finally, I open the vent fully to allow the smoker to pick up a draft and pull the reloading charger out about 1/2 inch. Like a flue in a chimney.
Close the door and walk away for at least 30 mins. before checking to see if it’s working, the more you open the door the more you are interrupting the air flow. Don’t hurt yourself by continuously checking to see if its smoking, you are interrupting the proper air flow.
I have also noticed if at all possible I will set the APMS up on a rack instead of the bottom left corner. If I have the room, I place it between the reload tube and the vent and it always works there.
Hope it helps!