Category URL’s are missing forward slash after domain name

What is in your “Category base” filed in admin > Settings > Permalinks?

Nothing is there. The field is blank.

Just as a workaround: try to put there this: “/category” – without the quotes, of course.

That worked. Thanks!

As I said, it is not a real solution because we didn’t eliminate the cause of that erro… but at least it works until you figure it what the real issue is. Glad it worked. You may want to mark this as resolved.