XF 2.1 Likes on posts not visible after 2.1 upgrade


Active member
Recently upgraded a forum to 2.1. After the upgrade, all Likes on posts from before the upgrade are no longer shown below the post.

The Likes are still there, and will visually appear again after the post is liked by any user, and remain visual to everyone afterwards.

I assume this is a matter of a cache needing to be rebuilt, but I'm curious which one it would be?