Hello,

Thanks for reaching out. Many beekeepers have trouble seeing eggs in cells. New beekeepers often have to train their eyes to know what they are looking for. It helps to have the sun behind you so that the light gets into the cell. The eggs look like tiny grains of rice at the back of the cells. Some people can't see eggs because their up-close vision isn't sharp enough, and they look for young larvae instead.

Did you see larvae (open brood) and pupae (sealed brood)? If so, it might just be that the eggs were there and you weren't able to see them. If you didn't see open brood at all, then your colony may be queenless.

If you suspect your nuc is queenless, you can try giving it a frame of eggs from another colony. If your nuc builds queen cells it is likely queenless; if it doesn't build queen cells then it likely has a queen or is in the process of requeening.

Here is an article on queen issues. 

Feel free to reach out with more information and questions. Best of luck with your nuc!