Try these tweaks... it can take 3 days, and accepting the apology is important. Another victim or nipping realized that she wasn't yelping loudly enough... and blew a whistle... You really need to get a startle out of the dog, although you don't want to scare him... just a small surprise... so that he says, Huh! ...before he goes back in for another nip.
The Bite Stops Here takes about 3 days to kick in, even then you only get a reduction of bloodletting, slowly resulting in bloodfree nipping, leading to mouthing, etc. Depending on the reaction of the pup, you don't have to use a Yelp!, you can say Ouch!!!, or Oops, where you want a marking word, to indicate when you are withdrawing attention.
Re-read the Sticky:the Bite Stops Here. perhaps you need to try a little longer. Read this and note the 3 days and the apology....maybe, he ignored the Yelp!, because you ignored the apology. Instead of the Yelp, you can say Ouch! or Oops!
Some Tweaks to Bite Inhibition (to get him to stop biting when he wants to play or otherwise):
1. When the pup bites, then yelp. It should sound about like what the pup does when you step on its paw... don't step on his paw for a sample

. When you yelp, the pup should startle briefly and stop nipping. (Look for the startle) Praise and pet. He'll bite.
2. When he bites the second time, Yelp. When he stops, praise and pet. He'll nip again, although it may be a little gentler. ...
3. Whenshe bites a third time, Yelp (see a pattern?). But this time, turn your back for 15 - 30 secs. If he comes around and play bows or barks, then that is an apology. This is important. Accept it, praise and pet... and cringe in expectation of the next nip...
4. When he bites the 4th time, Yelp, then leave the area, placing him in a 2 min. time-out. It is better if you can leave, rather than moving him. Then, return and interact. (He's still hungry...)
5. When he nips the fifth time, yelp, and leave the area, stopping interaction for now.
You can modify the number of steps, but not what you do... for example, you can leave in a huff

, after the second nip or even the first, but you have to provide a vocal marker, to give him something to react to. I still use a light yelp with my 11 yo when he lets teeth touch skin as I give him a treat. No pressure or harm, but I want him to appear very safe to everyone.
Pups need to sleep over night in order to learn their lessons. So, keep doing this for 3 days. By the third day, you should notice signficant Bite Inhibition. He may still nip, but it will be softer and he won't draw blood. And, he should be less aggressive, especially, if you notice the apology. Keep up the training and make sure that everyone yelps.... Very powerful method.
If you learn the technique, then you can apply the "yelp" to other circumstances, also. I believe that "yelp" is "Please don't do that, I don't like it." in dog communication. I currently use the yelp when my dog plays tug, then runs with the toy, when he fetches and keeps it out of reach or when he takes a treat too quickly....