If this is the first time you've done this, or the first time you've done this in a LOOONNNGGG time, it might take longer than you think.
Or - you're just testing at the wrong time. Which is more likely.
Lot's of water or lots of exercise will give you a false negative on your ketostix. Not sure what your schedule is, but if try it in the early evening, about an hour after your first meal of the evening (i.e. dinner time) on a day when you don't work out, or BEFORE you work out. Lots of water dilutes the urine and exercise tends to burn off ketones, so that there aren't any left to register on the stix. I've turned the damned things mauve after dinner and then worked out and tested shortly afterwards and got NADA.
On the other hand, you could be the victim of the dreaded "hidden carb". Suspect your condiments first, sauces, mayo, ketchup, artificial sweeteners, cream in coffee, salad dressing, etc. Anything you put on your food that isn't the food itself.
Remember, that just because your burning fat, doesn't mean you'll register on the stix. And just because you register on the stix, doesn't mean you're burning body fat (dietary fat will register, too).
So...
1) give it another day before losing hope.
2) make sure you check at the right time.
3) look at the labels on your condiments, make sure you are indeed under 20. Tho, most men will go into ketosis as high as 50 if they are relatively active.
Fawn