There are three new big features in fastpages, one of them involves a breaking change that doesn’t allow for an automatic upgrade via opening an issue. The best way to get these features is to copy your posts over to a freshly created template. The below are all screenshots from the README
BTW: I still find fetching from remote and fixing conflicts manually relatively easy. This way people can keep their custom stuff, e.g. index.html. Just a little tip for anyone that prefer a different approach for updating.
I pulled the latest changes yesterday. Unfortunately, I am actually facing an old error that we fixed, local images that are used in notebooks are not found in posts.