As stated on the bonus terms, "to all eligible sportsbet-io players", not "eligible to all sportsbet-io players". I believe it's a limited event, and you happened to join without being eligible to it.
If that is the case, then the OP didn't break any promotional rules like they said and the fault was from their own end, they have also not explained what makes a player "eligible" for this promotion, maybe that will also help us understand why they claim OP is ineligible.
That said, I believe the right thing to do would have been to compensate OP in one way or another, it is not his fault, he was allowed to "opt in" for the promotion, and he competed with others until he won something, maybe your contact can arrange a compensation for the OP right?