Time to let them go.

[GotButterflies]

Crabs love to dig and hang out just as much as they love to climb. They won't suffocate as long as you don't bury them. If they dig the tunnels themselves and put themselves underground, then they will be okay. When the crabs are underground, be sure not to add anything to your tank. You don't want to collapse any tunnels or caves that they might have built. Sometimes I don't see my crabs for days, but I know that they're there

[Alyw77]

Thank you. One went under right away. Haven’t seen her. The other one is out and about. Even when I open the cover to add food and water.