Categories not being displayed

We’ve added Most Popular Tags as a widget on our sidebar to show the most popular Categories. Our clients have been complaining though that the list is empty, meaning no categories were being shown despite us having categories set on the site.

Some of my colleagues also told me that the categories weren’t showing, but for some reason, it shows fine on my end, which makes it harder to fix. They are using Chrome and so am I, and an interesting observation I had is that they seem to have empty categories on their Chrome but mine is fine, but Microsoft Edge also produces an empty category list for me.

What seems to be the cause for categories to be empty on other people and not on mine? How do we fix it?

Thanks.