How close is your set temp to your room temp? You may have to raise it up 5+ degrees to get it cranking for a while. If it's close, it may start backing down as not to overshoot the temps. It the way the coaltrol works to maintain temps. Coal take time to heat up, it is NOT instant like gas or oil. SO, it may take a while to really get cranking. Normally an hour or so.
My hyfire, I run 46 Max, but your 6 and 40 is a great start to get it going.
Where is the stove located? (basement, living area, etc..) Where is the Thermostat located? etc...
Get a stove (Magnetic) thermometer, and check the stove front, pipe, before and after the baro, etc...and a manometer to check your draft accurately. On your baro, where is the weight set?