We're running into challenges with videos and proof. Is there a maximum video file size that can be handled by proof? Can you combine multiple videos into one proof? How successful are the results if combining?

what are the challenges you're running into? I see that the help article says there is a 4GB size limit https://one.workfront.com/s/document-item?bundleId=the-new-workfront-experience&topicId=Content%2FReview_and_approve_work%2FProofing%2FCreating_Proofs_within_Workfront%2Fsupported-proofing-file-types.html&_LANG=en

However, I also spoke to Support about it a few months ago, and they explained that it also has something to do with the stability of your connection (so if your internet connection is flakey, you may find this prevents you from uploading files even if they are not near this size limit).

If you are experiencing problems with the proof generating on your uploaded file, I would suggest you submit a Support ticket, as they can probably help you identify what the problem might be.

PS: I just checked, and looks like you cannot combine two MP4s. They will just upload separately.