It is common for the female to test the male by nipping his fins. The female wants a nice strong male that can defend the nest because only the strongest and smartest survive in the wild. She probably nudged his side first to entice him to wrap her and she nipped his fins when he did not do what she expected. She may have rejected him. If she is not head down in a submissive posture it might be a good idea to try again in at least 2 weeks after reconditioning. You could also try another female after reconditioning.
IME, it is not uncommon for male betta imports to be TDTB(too dumb to breed).