You should make sure that on Output page your Bank(Channels) for channel 2 is set the same way as the others. And of course that motor #2 output page looks about like the other motors on output page.
If that does not fix it, you can go to Vehicle page and set NE arm/motor to use output #5 instead of #2. Save, move ESC connector from #2 to #5, reboot (maybe not needed), go to output page and set NE #5 up again.