You probably cannot insist that they allow your name be added to the deeds.
It is worth asking why you would want your name added.
As a married couple in their principal residence, you as the spouse, already have extensive rights over the house, and as you are not on the mortgage, you have no liability. Obviously from a practical point of view you have been paying the mortgage up to now. But you have no legal liability to do so, that surely is worth something.