"Unspay/Unneuter" option unavailable?

Hi! I adopted two dogs (one male and one female), and they both happened to be spayed and neutered. I took them both to the vet to have them unspayed and neutered so that I could get some puppies, but the option is grayed out. However, the spay/neuter option is available. I tried having them spayed and neutered, hoping that the option would be available afterwards, but I still can't do it. Looks like a glitch? Any way to fix this?