I was having this problem but what I noticed was: check your distance to the opponent when you do the 214D~C 5C <- some characters require you to be close to them while some others don't. Be sure to see how high above the ground they are too!
Also, I can't, by all means, do the following:
5D~D j.2C 5B 3C 214D~C 5C (j.C)x5 2C 4D~D (j.C)x5 JC (j.C)x5 j.214B
They tech after the 2C tho if I use the 214D~C 5C 2C 4D~A 4D~D (j.C)x5 214B variant I can make it work. Thoughts?