Beers been in bottles for 2 weeks now sitting at a constant 68 degrees. Just popped the second one open and they've both been slightly carbonated but nothing great. No head at all. I used 4 oz. of corn sugar. It was a 5 gallon batch.
If you have a chest freezer or fridge, place the bottles on top. I've had the same issue with a Zombie Dust I made. It took forever to carbonate. I brewed these in December and some of the bottles are gushers and some flat.
You can also turn the bottles upside down and mix up the trub at the bottom. I had to do this and with putting them on top of my freezer I was able to get them bottles to carbonate.
I now use a sanitized spoon to mix up priming sugar once added to my priming bucket.
I hope you mean on top of the fridge, not inside!
Place some place warmer, maybe 72F or so. Or just wait. It will carb eventually. You may shake the bottles a bit to make sure yeast is in suspension but temperature/time is the key.