It's normal that a 14 year old child does not arouse you sexually although you seem quite disappointed by it.
Actually, what is "normal" is that males are aroused by sexually mature females. It has little to do with chronological age in years, although there are obviously rough age boundaries around pre-pubescence, pubescence, adolescence, and adulthood. Some females (and males) mature earlier, some later. The peak of sexual attractiveness in females is somewhere between 18 and 25 for simple biological reasons.
A male who is aroused by a sexually mature adolescent is not abnormal physically, he is just allowing his gaze to wander outside the bounds of social convention. Those conventions change, and it was less than 75 years ago that musician Jerry lee Louis married his 13 year-old cousin.
A male who is aroused by sexually under-developed females (probably the best definition of "child" in this context) has an actual problem.
And a 54 year-old guy like me who brings any of this up is of course pretty creepy.