My guess would be that the attic fan's motor is shot. Some motors are sealed, some have a lubrication port. My guess is if it has the lube port it hasn't been maintained. Regardless its likely a goner.
if the motor is separate and uses a belt to drive the fan you may be able to replace just the motor. My guess is the cost of a replacement motor would be similar to a whole new fan. Same with a motor repair.
As for 'makeup air' - yes, you should have makup air. This can be in the soffits, the ridge or in an opposite gable vent.
Look first at the soffits, from the outside. If you see vents go in your attic and make sure they are not blocked or covered by your insulation. If they are get your insulation contractor back to re-do his incorrect installation.
If you have no soffit vents, no gable vent and no ridge vent - you need to add something. Gable vents, if you have a place for them, are easy enough to install. Ridge vents are easy too if your roof is not too steep.