If you are not using enough of it, it won't be able to lubricate or help your vagina. Sometimes if women are really dry up there, the tablet can't dissolve properly and so isn't effective... The resistance is probably that you are very dry up there.
I'd agree you should try increasing your dose to every night and adding in estriol cream as well, and also vaginal moisturiser like YES...
You might also want to consider systemic HRT (or an increase of it, if you are on it) which will help. The vagina is the canary in the coal mine. If it's this dry, think what's happening elsewhere in your body...