For each impression, there is a field called ‘b-cat’ (blocked categories) included in the request that allows the publisher to block creatives with content in certain IAB categories. If the IAB category assigned to your creative in the audit is included in the list of blocked categories, your ad will not be eligible to serve on that inventory. In the CTV landscape report, the request_bcat column can be found in the sample logs for each deal. While this is just a sample and blocked categories could vary for each impression, this provides insight into commonly blocked categories by Deal. If your creative category is blocked in all sample impressions, it is unlikely you will be able to run through the selected deal.

These categories come from the Open RTB Specs, that can be found here in table 5.1 ‘Content Categories’:

Open RTB Specs v2.5