"Not Processed" Error for Adobe Admin Console migrations

Hello, 

I am a technical specialist and I assist clients in performing migrations from VIP->LGA on their Adobe Admin Console. The "Troubleshoot Bulk CSV Uploads" helpx guide includes documentation on how to resolve various errors, but sometimes after performing these migrations I get a "Not processed" error, where 0 users are migrated with zero insight as to why, and nothing within the Adobe documentation I have found explains this occurrence. If there is a guide that explains this issue, please let me know. 

If I had to guess, I would suspect that the enterprise-type console throws an error when it sees Adobe IDs (which a lot of my clients are still utilizing) as opposed to Business IDs. But if this is not true, then I am completely baffled why some migrations I perform succeed without issue, and some fail for seemingly no reason.