It looks like I have full affinity with Arthur but I can’t access the little heart that usually at the top left corner of the shop scene for the heart event.
I have a different problem. I’ve bought everything before the affinity thing so now the only way to build it up is to battle him for tiny bits at a time
sometimes with updates it'll say the affinity is full but I wont have access. Usually this can be fixed by just buying one more thing from that person ( the cheapest thing ) or for ppl you can't buy from, battling them once.