I recently bought the ezrun 35A esc and the tacon 4400kv motor. Plugged it all in and it ran fine. The programming card worked. Changed and played with the settings and the car ran fine forward, brake, reverse.

Afterwards I decided to calibrate the thing. After calibration end, the motor blipped once. After that it just does not spin. The esc is delivering juice to the servos and all since they work. However, the motor just does not spin.

Any idea what could be wrong?

So you ran it before calibrating it? Then you calibrated it and it stopped working? It sounds like you did not complete programming correctly. I would check all connections closely and try programming again following the manuals instructions. These are very reliable ESCs, and most problems can be traced to a user error, but occasionally a bad one can find its way into our hands. However, since it worked before you calibrated it I am pretty sure it should work again.

Does the battery still have enough charge ? Maybe the ESC reached the low voltage cutoff.

I did complete the calibration as per the manual. And i tried 3 different packs all fully charged. Still nothing outa the motor. Even tried an old fm radio receiver in case the 2.4 GHz was causing issues. I will have to call hobbypartz monday first thing to get it resolved seems like.