If the yoyo is unresponsive it’s you. I can only think of one problem. Are you tugging the string with your throwhand like a bind? Are you whipping the loop so big that it binds?
When your string hits the gap, let it be and just let the loop come around. But do not tug the string on your throwhand whent he string hits the gap because that motion is exactly like a bind.
Also if you whip the string to your throwhand size too much, causing the loop to be bigger. Yes bigger loops are easier to catch but if you don’t catch the big loop, it will bind, snag, or be knotted up.
Now, with the trouble about not hitting the gap:
You want to parralel your throwhand and the yoyo so that it is in a line. So when you whip, the string will always get to the gap. Whip to your throwhand side more too but don’t bring your throwhand too close to the yoyo. Having the hand closer to the yoyo when whipping causes a bigger loop and having a bigger loop (as stated above) will either snag etc. It is ok to try it though. For me,I don’t do big loops. Also, just practice. I was hitting the string 5/10 times and now I hit it 9.5/10 times.
So good luck and have fun!