Giveaway suspended

You should have opened a support ticket not a thread

You can change between received and not received, actually getting people to do that however...
Try leaving replies to the winners somewhere.

A giveaway winner can always change the feedback from not received to received anytime in the future. If you click the "Sent" button on your giveaways created page, they normally get a notification on the top of the site letting them know they won a game, but I'm not sure if that will happen after they have already marked it as not received. If they commented on your giveaway, you can just reply to them, but if not, you can try adding them on Steam or find a way to contact them here on steamgifts since we do not have private messages. To get their attention here, you can send them a message on an old giveaway they created letting them know what happened.