She could also just be a dud queen.
Haha true. Occam's razor strikes again.
I think antdrew is right, can queens just stop being fertile?
I guess so? I mean it could happen, genetically or otherwise. Never experienced a queen successfully founding a colony and then just stopping, but maybe it's a rarer occurrence. Bad luck, I guess.
I also read from the link you gave us, and it does clearly state: "queens may stop laying eggs if the food supply is insufficient." So I guess it could be something like that, a food issue.
Manica invidia (1 queen, ~200 workers)
Manica invidia (1 colonies, 1 queens plus 3 workers)
Lasius niger (single queen, ~200 workers - naturalistic, predatory set-up)
Lasius americanus (1 colony, ~10 workers)
Tetramorium immigrans (3 colonies, 3 queens, ~ five workers each | 1 colony, 1 queen, ~1200 workers)
Formica aserva (aserva queen, ~15 Formica neorufibarbis workers)
"And God made...everything that creeps on the ground according to its kind.
And God saw that it was good." - Genesis 1:25