I apologize if I’m necro-ing unacceptably, but I had this exact issue with my YYJ classic upgraded, so I feel like it’s relevant. Even if OP has already figured it out, it may be helpful to others who come across this.
The trick for me was to start out by lowering my throw hand very close to the yoyo after mounting, and make sure to pinch the string with my opposite hand, then pulling up with my throw hand and letting go of the pinch.
You have to let go of the pinch after you start pulling, and you need to make sure the string between the yoyo and your throw hand has no slack before you let go of your pinch (you’ll feel the resistance of the string starting to wind.)
The timing of everything can be tricky, so it helps to start with slow and intentional movements and speed them up as you practice.