Hi jdsilva,
Thanks for the explanation and the link. I have also realized the forwarding/blocking is only shown when the port is up, and if the port is down you can only see if STP is enabled/disabled (which is obvius and I didn't realized before when I open this post). Now I have selected an interface which is up and I can see it is in forwarding state:
This is also stated in the link you provided:
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Thanks again,
Julián