Q. 8 yo small dog started urinating on one sofa during the night although she has access to outside via a catflap which happily uses during day.
A. Have her seen by your vet to rule out medical causes such as UTIs. Reinforce crate training (again if necessary). The crate should only be big enough for her to stand, turn around and lay down. Put her on a strict schedule of going outside or being let outside. Take up the water 2 hours before bedtime and take her out right before bedtime. Restrict access to the room with the sofa or crate her at night. Be patient. Be consistent.