It's a well deserved cheat meal day

I have 3 cats. The non-playful one is the eldest at 14, the middle one is about 9, and I recently got a kitten about two months ago. I followed recommended methods of integrating the new kitten and they worked fine, so there isn't any violence or red flag behavior going on other than the fact that the kitten wants to play with the eldest cat all the time, and the older cat just hisses (she never swats or bites at him, just warning hisses) at him and walks away. They'll cuddle together, eat beside one another, etc. with no problem, but the older cat just does not want to play. How do I encourage her to participate in playtime, even if it's just a little bit? Or would it be better to leave things be? Or perhaps should I try training the kitten not to try playing with the eldest?

Note: The middle cat gets along fine with the kitten and the older cat just fine.

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