My Kitten Won't Eat. What Is Wrong?

First off, you need to feeding high quality, high-protein kitten food... Please, don't skimp here—this is a rapidly growing kitten and right now, the quality of food is more important than ever.
At 8 weeks old.. He's certainly capable of eating regular kitten food.. But as long as he's getting enough formula to satisfy his hunger and nutritional needs, he has no reason to make the switch (if given the choice, would you rather eat ice cream or broccoli?) KMR (probably the same company making the kitten formula you're using), has a product out called Second Step Kitten Weaning Formula.. If you haven't, it's time to switch to 2nd Step 
Leave a dish of kibble and water out all the times... Once a day for the first week, continue to offer the kitten formula.  Then three times a day offer a saucer of the 2nd step mix, following the progression directions on the canister.  After about a week, mix in a few pieces of dry kitten food that has been soaked in water and mashed up into the mixture... Do this three times a day, even if the kitten refuses it every time. Put him by the food each time... If he is very stubborn, stick your finger into the goop, then allow him to lick it off... If that doesn't work, gently hold him in place and rub a little bit on his teeth to try and get him to start licking from your finger.
Once he starts licking the mash from your finger, lower your finger until it is in the dish. He should then start to eat from the saucer... Then gradually reduce the amount of formula each day and increase the amount of moistened kibble until he is just eating the kitten food. Gradually add some canned food to the gruel, and some pieces of un-soaked dry food, reducing the amount of kitten formula until you have eliminated it. You can continue to feed the kittens a mixture of canned and dry kitten food for a while.. But try to get him off the wet food by 6 months at the latest.  
Don't be surprised if he experiences temporary diarrhea... As you know, kittens have very sensitive tummies and any change in diet can cause loose stools... Be patient, and keep trying — he won't starve himself, and he will eventually catch on.