Does the queen have room to lay eggs? If all frames that she has access to are filled with honey, nectar or pollen or brood, she can't lay eggs. Add another box or replace a honey frame with built out comb
Is there a dearth? The queen will slow down if there is not enough food to go around
Do you see queen cells? If they are capped, then the colony may have swarmed and are waiting for a new queen. You may also have a virgin queen present. If a new queen is added, the colony will kill the new queen.
Do you still have open brood? Brood gives off a pheromone that quells a laying worker situation. Check for queen cells.
If you have another colony, take a frame of eggs and larva and add it in. Check for queen cells in a couple of days. If you see queen cells, then they are queenless.
Do not let a broodless situation go for too long. This may end up as a laying worker colony.
Adding a new queen usually does not work and they will end up killing her. In this situation, merge the colony with a stronger colony to disrupt the laying workers. After a few weeks, once the laying worker situation is resolved, you can split the colony and introduce a new queen.