Its human nature for many to want most what they can’t have and this can be used to manipulate many submissives.
If your sub, does not show a clear indication of the privilege they enjoy from licking your pussy, try telling them they are banned for a couple of weeks; perhaps a month. Don’t let them get anywhere near your body. I think you will find they then genuinely beg for the privilege and are grateful forever more, under the constant threat of another period of denial.
The same tactic can be used for many things. Moisturising your body, washing you in the bath, brushing your hair, giving a pedicure, etc. And their humiliation is delightful to witness when they find themselves genuinely begging for such ‘privileges’. It seriously helps keep them subjugated to their lowly status too.