Welcome to the Let's Encrypt Community, Renato 
Firstly, let me share some wisdom: avoid using --force-renewal like you would avoid a deadly disease. It almost never results in anything useful.
That said, it looks like your certificate was originally obtained by fulfilling an http-01 challenge using the webroot authenticator and should have autorenewed the same way if the webserver configuration had not changed since April 5.
Certificate history for justdance.dei.uc.pt:
https://crt.sh/?q=justdance.dei.uc.pt
Is there a reason that you are now trying to manually fulfill a dns-01 challenge?
Let's try something. What is the output of this:
sudo certbot certonly --nginx -d "justdance.dei.uc.pt" --dry-run