Thanks, @david. After checking that option, I see no difference. I get the exact same message for both invalid and private URLs. Maybe it’s a translation issue, as I am using Spanish?
Here is an invalid URL: https://comunidad.ebrolis.com/cvdscvsd
And here is a private topic: https://comunidad.ebrolis.com/t/presentaciones-de-los-coaches-autores-de-los-libros-del-pack/383/8