Both hens have laid eggs on the floor
Last night was there first night in there
I tink rosemarythyme makes a good point, they may not have even found the nestboxes yet.
Since there are only two hens, you could just pick them up and stick them in the nestboxes.
If you put them in headfirst, then they will turn around and come out, and hopefully they will decide that it's a place worth looking into. (And even if it doesn't work, it's probably pretty easy to try for just two hens.)