My 2 cents….
Somehow, it's possible the crystal on your fc when batty… don't ask how, why or whatever…. Change the crystal on fc. That should hopefully fix your pairing problem.
But! Make sure you replace it with the same value crystal.
Anytime I've gotten some stupid idea to drop $20 on a toy quad, it never fails… I always end having to replace crystal with new. Smh.
Helpful friendly advise…
Save up just a little more money… get you an entry-level name brand RTF kit for like nada to really get you in the right direction.
From there… the sky is literally the limit.
Good luck.
Have fun!