Monoprice maker select v2 doesn't extrude but is not clogged
Try advancing the extruder manually using the control interface. Extrude about 10 cm of filament to verify that everything is OK with the machine.
Is the filament curling on the way out of the nozzle? If so then there may really be a clog and you should clean it. Invest in some cleaning filament as well.
The idler bearing may not be pushing down on the filament tightly enough. Check that the spring which holds it in place has not become soft or broken.
The drive gear could be dirty. Plastic particle build up on the gear will cause it to slip. Clean the drive gear to remove all plastic build up.


Outside of this you could have a mechanical problem with extruder. Advance the motor using the control system (without filament installed) to verify that it is working properly.