Filament not coming out

I have an Crealty ender V2. The nozzle temperature is set to the default of 200, and the bed set to 60. When I print, the print was coming out 'stringy', not at all, or the extruder was dragging the filament all over the bed. The bed was leveled at least a half dozen times, and I even increased temperature of the bed to 65 and the nozzle to 210 and when it prints, it still does the same thing. Now with that said, if I take off the blue knob while printing, squeeze the lever to where I put the filament into the hole to feed it, and push the filament in by hand, then it prints fine! Nice thick filament comes out and sticks properly. If I keep pushing that filament in the entire time, it would be printing perfectly. But if I let go, the filament stops coming out again, or the extruder drags it around, or it's stringy again. Can anyone tell me why? I don't think it matters but I am using Cura to do the slicing. I've even taken the filament out completely, and re-feed it back into the hose. Thank you

Sounds as if the extruder gear teeth could be clogged up from filament grinding.
A you tube search will probably give you some examples of that.
Also check that filament can be pulled from the reel as freely as possible.