Guardian has built-in denial for self-employed individuals

I have had a non employer Guardian LTD policy since 1991. It is for full disability. I have never had a need for it. Now that I do, I am finding they are doing all they can to deny this claim. I am self employed in the trades. The majority of my work is field work with “office work” to bill and deal with materials, etc. My injury prohibits me from doing field work. They are saying that since I do office work I am not totally disabled and, therefore, not eligible for benefits. Unfortunately, without field work there is no office work. The policy is for a stated amount per month after the elimination period. Now they are asking for my tax returns. It seems to me they have defined a built in denial for self employed individuals.