TRPC & Optimistic Update

I'm trying to implement optimistic updates with TRPC using the simplest of examples from the docs and haven't had any luck: From https://create.t3.gg/en/usage/trpc, I'm doing a parallel example where I have 'upvotes' instead of 'posts'. I've attached the schema that works and the router that also works. The only part that isn't operational is the optimistic update (Error messsage attached, Symbol.iterator) Any help would be greatly appreciated. Optimistic update is obviously a nicer UI to have