extruder ball-up

Hi, i am new to printing.my printer has doen about 15 prints, and now it starts to ball up the filament under the extruder, isntead of sticking to the glass bed. i have washed it, to make it completely clean, i have put down stick glue that came down with the printer, but it will not stick to the bed.i am using PLAWhen i start printing, it can sometimes stick to the glass before it losens. either that happens or it just curls and balls up under the extruder.I had the machine working fine. but then i was stupid enough to let my coworker be allowed to print stuff, and when he was done "calibrating it" and finished his print and i was to start my own... i couldn't get the PLA to stick to the bed and it just curls up under the extruder.

i have tried getting the bed closer, i have tried making the glass clean, and i have tried to make it stickier with the glue that followed with it.

seems the reason was the PLA itself not wanting to stick to the bed, when changed to a different color from same supplier it stuck to bed.