I sent an invite to a friend last year, but the email didnt arrive to him, I dont know if it was a problem with his email, but I lost the invite anyway... How I can solve this?

Dear Gabo,

Simply send a new invite. The invites expire after 3 days so if it was a year ago you should be able to resend without problems. Yes you have received the invite back in your account already

Tell your friend to register right away and not wait longer than 72 hours.