BBF issue

I bought my D7200 about 3 months ago, about a month ago I set up BBF, it was working great, but for some reason, now somehow I lose focus lock, and the shutter won't release 100% of the time, somehow it appears I lose focus, according to the focus indicator in the viewfinder, I wonder if I changed a setting inadvertently. I set up a4 to AF-ON only, and f4 to AF-ON. I primarily shoot in focus mode AF-S S. Any Ideas as to why this just started happening?

This is a good article and short video on BBF, worth a look for sure.

https://nikonrumors.com/2014/01/25/how-to-use-nikons-af-on-and-back-button-autofocus.aspx/

Is it set for release (which will take the photo even though it might not be quite in focus) or is it set for focus priority? It's somewhere in the settings menu--sorry I don't know where. I tried out BBF once but it wasn't for me. I'd check that first.

For the technique to work as most would expect it to work, you need to be in af-c mode with release priority. Being in af-s with bbf, you won't be able to release the shutter if you recompose. Using the technique properly, you won't need to use af-s mode. You hold the back button for continuous focus and release it when you don't want focus. Releasing the back button is a pseudo af-s mode. That is the beauty of the technique, you have continuous focus when you hold the button and have the benefit of releasing the button if you want to recompose. Focus-recompose is normally impossible in af-c mode, but the bbf technique makes it possible. Its on you to assure focus is where you want though, the camera will fire regardless of focus.

Thank you very much