I think you need to add the rule further down the page under port forwarding. You are trying to add a rule under the IPv6 section. The silly thing is the ability to add IPv6 rules still shows even if you have IPv6 disabled...
![Screen Shot 2022-10-28 at 7.52.07 AM.png Screen Shot 2022-10-28 at 7.52.07 AM.png](https://community.meraki.com/t5/image/serverpage/image-id/26381iC5FF8EFA95FE85A5/image-size/large?v=v2&px=999)
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