VAST error 901, aka General VPAID error, is an error that can be caused by any VPAID error, which could be any of the following (1) SSP VPAID wrapper not buying (2) SSP VPAID wrapper timeout (3) VPAID creatives required insecure mode (4) An Ad Exchange “IMA Adapter” tag is used with the IMA SDK, and a VPAID ad is returned (the “Direct SDK” tag should be used). to fix the error, the publisher should ensure that any VPAID creative requests are supported for devices and players using the video creative profiles to control which creatives are eligible to serve. The buyer should ensure that any VAST responses that return HTML5 VPAID wrappers from IAS/DV/MOAT include an MP4 asset, and that the wrapper is not aborting playback. Also, ensure that you don’t bid on impressions without a determined advertiser or buyer, or attempt to initiate a client-side resale.