Not all sponsorships are for every platform. Some are Twitch Only, some are Youtube Only. This could be why you are not seeing all the sponsorships available.
Additionally, sometimes when a popular Twitch creator is trying to attach a Youtube channel they just started, it won’t show up. This is usually because the secondary channel doesn’t meet the Catapult requirements. Youtube channels won't show up on our platform if the following is less than 1000 followers.