float test, fill the sink up full with luke warm water, let sit till still, drop egg in and see if it rocks, moves or does anything..look up float test online
My only advice would be to give it a couple extra days in the bator. I had an egg I was about to give up on. All the others had hatched a couple days previously. Just as I was about to turn off the bator, I noticed a little pip. A few hours later, a tiny bird hatched. It's doing great and growing so fast - and I shudder to think I almost tossed the egg. It was a dark welsummer egg - so, even when I candled it, I couldn't really tell whether or not anything was growing in there.
I always use the float test and find it very accurate as long as you know your temps were okay and you're just checking one or two late eggs out of a bigger successful hatch. If you haven't had any of them hatch out yet and you suspect your temps might have been low, it's not as useful.
You can float an egg safely as long as it hasn't pipped. Do it in water that's 97-99F, so it doesn't lose or gain any heat. What you're looking for is ripples in the water showing the chick is alive in there and wriggling to begin the hatching process. If you see that you should expect a pip within the next day. If you don't see ripples and the egg is floating but not moving, that doesn't necessarily mean that the chick's dead. It might be dead, but it might also be alive and perfectly healthy, and just not sufficiently developed to be wriggling round into position for hatching yet. That's why floating eggs that have had low temps isn't so useful.
I nearly killed a late egg this way once. I had 6 under a broody on day 24, and only two of them were wriggling when I floated them. I was ready to toss the other 4, and they'd been out from under hte hen for about half an hour, when I saw a tiny faint twitch from one of them. I warmed it up and stuck it back under the hen, and it went on to hatch fine on its own and grow up perfectly healthy...
I was on day 23 and was going to pitch the three eggs I had left in the incubator. I picked one of the eggs up and I heard peeping. What a surprise. It had pipped on the bottom side of the shell where I couldn't see it. I did help it hatch and now it is doing great. Keep the faith...