Does everyone respond to hypnotherapy?

Anyone with even average intelligence and a bit of imagination can be hypnotized to one degree or another. Once hypnotized, if the therapist knows what they are doing, therapy can be conducted in a way that works best for the client.

There is a range of susceptibility to both hypnosis and hypnotherapy, but in general, "yes", virtually everyone will respond. In some cases, a person may be only capable of only light levels of hypnotic trance, but the good news is that most therapies can be conducted at even Stage 1 on Arons Scale of Hypnotic Depth.

Hypnosis almost always requires a willing participant. If you actively resist or work to prevent trance, then you would be the exception to this. You can actively resist being hypnotized and there is virtually nothing I could do about it.