Works fine for me, also Spain, Vodafone as the ISP.
Edit: eeh, that's a different site than the one mentioned by the submission, why it wouldn't work?
Edit2: Also, the error is wrong and server-side. If your ISP is trying to block the website, you'll get either a tls error that the certificate isn't matching, or for non-https sites you get redirected to the scary "You're contributing to something illegal blah blah".
Edit: eeh, that's a different site than the one mentioned by the submission, why it wouldn't work?
Edit2: Also, the error is wrong and server-side. If your ISP is trying to block the website, you'll get either a tls error that the certificate isn't matching, or for non-https sites you get redirected to the scary "You're contributing to something illegal blah blah".