Needing a queen
Can you confirm if they did have any brood about a month ago?
Do you see any empty queen cells? (this would be peanut-shaped cells that contained a queen at some point and they look as if the queen emerged from one end or was killed from the side)
Do you have any estimation about how many bees are there? (just for reference, a 3 -lbs package is about 10K bees).
We need a little bit of history to figure out what happened.
There are some overwintered colonies that swarmed recently, and they look similar to your description until the new queen gets mated and starts laying eggs.
If they are in the process of making their own queen, they'd reject and kill any other queen that wants to be introduced to the colony (they prefer the queen they rise themselves).
In most cases, they will make an emergency queen when something goes wrong with the existing queen. Even if they didn't swarm and the queen just failed/died, they tend to have some eggs to raise a queen.
When we opened the hive for the first time in April, I did see empty queen cells, but at the time i was just wanting to replace the bottom screen board, clean out dead bees and open the front entrance and remove the bottom box since the all the bees were in the top.
So on Sunday I did see larvae and there is capped brood and more worker bees maybe doubled in size from last week est 8000-10000 so decided to return the second box with frames with comb, honey and a few blank.
I looked for eggs but i have a hard time seeing them
I plan to do another inspection in a few days unless it rains