Preferred deals? Try raising the floor price / Check restrictions in ur targeting / Check if the native ads u set up comply with the pub’s format as well More on reddit.com

CPM floor is the minimum acceptable bid , CPM fixed is for when you have already agreed a CPM and you will be bidding only that for the deal using a fixed bid strategy. More on reddit.com

everything pretty much operates in a waterfall (even header bidding) and CPM is pretty much the competing point across everything (and sometimes publisher politics :) ). Direct sold generally sits above everything and will get the first look either because it's the higher CPM or part of the deal structure with the buyer that they get first look. Preferred deals are similar to direct sold whereby someone agrees to buy X impressions at Y cpm with the exchange being the place where the deal is brokered vs humans hashing it out. A preferred deal can (at times) have a higher CPM than the direct sold and will go ahead of the direct sold) Private auctions would be where a publisher sets a certain amount of inventory (generally higher up in the fall) available in exchange and only allows a small number of buyers bid on it and most times there's floor price set that's higher than the cost in the open exchange because the inventory is perceived to be more valuable Header bidding is suppose to create better competition and eliminate waterfalls but the waterfall part is only partially true in a lot of cases - the inventory sent to the exchange has already participated in a waterfall set by the publisher within their adserver. They have already said "this piece of inventory is priority 1 for direct sold, this is priority 2 and for preferred deals, etc..." all the way until it gets to a prioritization assignment for the exchanges and then that goes to the exchanges and the header bidding will do it's thing and try to find the best price for everyone. Hope this helps More on reddit.com

If it’s a 1:1 deal, a buyer shouldn’t need to apply viewability pre bids in platform. Either you’re providing quality inventory and that rail shouldn’t matter, or you’re not and that’s apparent in reporting, in which case they’ll just cut you. If they’re bundling a bunch of PMPs in an ad group so they can apply audience targeting, applying the viewability rail makes sense. Micromanaging a ton of individual deals for viewability when an in platform rail can just take care of it for you is a waste of a buyers time. More on reddit.com