What do you mean by "sleeping" ? Burried ?

African Bullfrogs are frogs who intend to burry several months per year (Roughly 9 to 10 months in nature).
So if your frogs burries, this is typical and normal behavior, especially for an adult.

When my frog burries, I wake her up to make her defecate if she didn't before burrying, or, to clean the tank.
Otherwise, if the tank is clean and if she has defecated her last meal before burrowing, I let her until she wakes up by her own. I only check periodically if she is still alive. This can be for several months...