If the cell is Capped they are about to swarm; normally when it gets capped they are off.
Do the number of bees look less?? It is possible they already have swarmed if that is the case.
You need a second set of equipment if you want to keep all the bees - ie if they have not yet swarmed.
always a good idea to have spare equipment to deal with these changes.
If they have swarmed you can only wait for the new queen to emerge and mate - min wait about 3 weeks before you see larvae and new laying.
This is why beeks need to check the hives once a week in “summer” when the bees are active from egg to capped cell is 8 days, another 8 for the virgin to emerge. She needs to be mate within 3 weeks or will become a drone layer.
You need to try and keep one step ahead, weekly checks are the way to go.
Have a look at the life cycle of the bees it will help you to understand what to look for.
Also look at swarm control so you are prepared next time.