Decades is gone from FIOS, at least in the Philadelphia area. The channel was provided as an over the air sub-channel or the CBS station. Now, it's a sub-channel of ME-TV's affiliate but Verizon doesn't carry it. They do carry ME and other sub-channels, just not Decades. Bring it back.
You can also reach out to the station that carries it and ask that they work with Verizon to carry.
it would probably need to be part of a contract negotiation