Hallo,

I just realized this:

A tag was accesible via 
www.example.com/tag/christian%20bale (I can confirm this, I have used it a lot).

However, the normal url for a tag is of this form:
www.example.com/categoryA/categoryB//tag/christian%20bale

I am not sure when it happened but the first global url is not working anymore throwing a 404.

Any idea?

Thank you very much

Hallo Fotis,

thank you for your reply.

I use K2 v2.10.3 on Joomla 3.10.2 version.

I cannot find "Adnvanced" but Enforce SEF URL character replacements is enabled.

I attach images

Thank you