Abilities don't register randomly.

I thought this used to be caused by my computer, but after getting a new computer, great specs and a new mechanical anti-ghosting keyboard, I think this is some gameplay bug I am having. I can post any specs you need, but my new computer is far above all the normal specs I've seen. My ping is 84 and for whatever reason, abilities just don't work randomly. Typically, this occurs when I am using a lot of abilities at one time or am close to death. I understand the close to death one could be ping, but I cannot combo standard combos that I know I know how to do. I am very confused and kind of at my witt's end with this game because I simply don't see how I can improve with these serious issues. Any help would be really appreciated!