In a state of being neglected and immobile, with no prospect of movement to a better place.
Limbo was on the border, not in Hell, but not in Heaven either, and ‘in limbo’ later came to take on the metaphorical meaning – ‘in prison’. Shakespeare used this in Henry VIII, 1613:
I have some of ’em in Limbo Patrum, and there they are like to dance these three days.
Soon after that, the meaning was extended to our current usage, which refers to any situation where someone or some project is confined and neglected, with nowhere to go until something happens to restart it.
All of the above quoted from The Phrase Finder