Attempting to add fiancé to my car’s insurance policy but GEICO says he can’t due to his own policy for a different car?

Hi all,

I have an SUV that my fiancé drives regularly. I’m attempting to add him to my policy since we live together and GEICO only lists him but won’t “activate” him as a regular driver onto the policy. Apparently because he has his own insurance for his own car? This doesn’t make sense to me, is this normal?