You don't mention which type or brand of powder you were using, but having a squeaky clean barrel shouldn't affect ignition.
There have been reports of inconsistent ignition and accuracy problems with some forms of APP due to age, storage and with using solid sticks versus loose powder. Is the powder sticky or gummy at all?
It's not the discontinued Goex Clear Shot powder, is it? Lots of folks complained about that powder!
Swabbing the old bore butter out of the barrel and making sure that the flash channel in the breech plug is open before you load the powder would help to insure that ignition isn't being blocked somehow.
After that, the performance issues usually either involve the powder itself or what happens during cleaning;
Powder fouling getting pushed down into the breech, or excess oil, solvent, water, lube accumulating in the barrel.
Some folks foul their barrel just by shooting off a primer, others don't take fouling shoots at all and prefer loading a clean barrel.
Are you shooting bullets with plastic sabots or plain pure lead conical bullets? What size/weight are they?
Some folks use wool Wonder Wad bore buttons under plain conical bullets as a gas check, or other types of over powder wads.
Covering the muzzle with tape or a balloon helps to keep moisture out of the barrel during hunting season. And bringing an ice cold rifle into the warm house at night can cause condensation to form inside the barrel which may hurt the powder. Many folks leave their gun outside at night to prevent barrel condensation.
Sounds like your powder may not be too good though. Are you cleaning out the flash channel?