"Cá huair?" was judged as using the wrong word, while cén uair was given as the correct answer. I would have learnt cén uair in school, but tried out Cá huair to remember it as an alternative.
Because they didn't set it as an acceptable answer. Please report it next time you see it.
The "h" before "uair" is not lenition, but rather a means to distinguish the vowels (and at the samet time the two words) "a" and "u" in two consecutive words from each other. As cén ends in the consonant "n" there is no need to place anything else inbetween.
(WHY?? Well you know the Irish pronounciation with many vowels together may get confusing, such as e.g. "aoi" in "daoine". It could be fun thoughj trying to figure out how to pronounce the construct cáuair ;- )
Ce an tam ata se, is how I learned to say what time is it . Why now is tha not correct?