Are they wobbling?
When you do the float test, you have to be really careful. A lot of people won't do the float test at all. Firstly Make sure there are definitely no cracks chips or holes in the shell. Make sure you use warm water. They need to be put in one at a time and they only need to be in there for 10 seconds or less.
What you are looking for mainly is movement. If there is still a live chick in there, it will wobble the egg in the water.
If they sit too high above the water line I think that means they are no longer viable, but check on YouTube, there are plenty of clips on there telling you how to do it properly and what you are looking for.
Good luck.