Ok, great, so we've established that he's eaten twice for you already....
Have you changed anything in his enclosure since he last ate?
Changes to environment can stress these fellas out a bit.
Also give some details of what your setup is like, temps, humidity, hides etc....
I would not worry if he has not eaten for 3 weeks, I had a ball that went 6 months and then just started up again.... they just stop sometimes.....
I'd still stick with attempting to feed him the way he is used to....
Good luck