I just got my first electric a MES 40 a few days ago. Get a $20-30 digital thermometer with the probe on the long lead, stick it inside somehow on the middle tray so the metal probe isn't touching the metal racks. fire the smoker back up and compare temps on the unit vs the external thermometer. From what I read these units are all over the place; some you set the smoker to 200 and its really 175, or some its 225 seems to be the luck of the draw. also use the units meat probe and compare temps too. Maybe yours isn't getting up to temp very well?
What kind of chips are you putting in there; fine shredded dust like, coarse chips about the size of a quarter to silver dollar? Use them dry, don't wet them. Last night that's all I did was dry run the smoker trying different chip types, amounts, wet or dry, etc. to prepare for my turkey smoke tomorrow am. Mines set to 275 right now for the turkey tomorrow. the MES display was around 265-270/271 on ave for the 2 hours I was playing with it, the meat probe was no more than +/- 8 deg from what the operating temp said on the display, and my external probe was only a few degrees higher than the display(s) on the MES. 268-278 was the most I saw on it... so it seems either they somehow got the MES running better or I got a decently accurate controller on mine.
I found that the fine dusty like chips smoked up fast and didn't last more than 15 minutes (all of my tests I only filled the hopper flush with the cutout on the tube, so 180 degrees worth of the tube if that makes sense. Also note, mine has the smaller ash tray (half sized, other side is flat with a riveted on cover) and the hopper tube is capped off on the middle so you can only load half the tube and I believe they made a retrofit for a double size ashtray and matching tube. What does yours have? The most consistent smoke (not crazy dense and not very light either) came from the chips, they lasted 22-24 minutes until smoke stopped, BUT when I looked in the tube they were a pile of black with only the edges faintly glowing, aka not making any smoke really, so I am not getting a full burn, somethings blocking the air coming in I believe.
When you look in the tube what do your chips look like they are doing?