nfc antenna coil wth external capcitor
This Antenna is good because of challenge to obtain accuracy of L and C.  

Note that this loop antenna is designed for two-way or Duplex mode of transmitter (Tx) and Receiver (Rx).  Each passive part can affect tuning as well as proximity to ground and connection wire impedance. 

Note that the final values of radio filter design are critically affected by physical layout geometry.

C1, C2 below are essential to the operation and should be C0G type or equivalent quality capacitors for temperature stability.  Note that a good balanced design is used so the C values are split into two values.  Balance makes common mode noise rejection possible.



Originally I said..

Did you use two 33pF for series resonance as specified?  

That is the proper mode, not parallel resonance. Ground proximity will affect tuning.

Did you make solder contacts?

The other parts provide EMC notches.