Page Property in Highlighted Contents stopped working

In a modern site, we have added a choice column called "Topic" to the Site Pages library. This column is used to filter the contents of the Highlighted Content webpart.

Until a few days ago, this worked fine, but now the "Property name" dropdown is empty. We have created a test page and added the same webpart and when pointing to the same column, the same thing happens, but it works fine on a different site.

What could be the reason that the Topic column no longer can be seen in the "Property name" dropdown?