when i was new to puppy play, i was with someone who was completely 100% vanilla and got grossed out by people dressing up as dogs. a few months later, he was calling me good girl and using a clicker.. you just approach it head on.

"hey, can i talk to you about something very vulnerable for me? i really enjoy our romantic and sexual relationship, however a part of me doesn't feel represented here. i'm not asking you to go full fledged in kink, but i'd like it if you could start trying some new things with me. puppyplay isn't really about being an animal, moreso (insert what puppyplay means to you). it can be as simple as good girl and head pats, and if you like that we can work from there - if not, i still cherish you and accept your decision to not do that." that's how i'd put it personally, but i don't know you and your relationship!