When you upload an email file for import, we run it through a deliverability check to make sure there aren't too many inactive emails in your list.
If there are too many inactive emails (more than a few percentage of your total list), we're not able to complete the import. Your best bet is to only import contacts into Hive you can send email to. This reduces the number of bounces and increases your deliverability!
If your import has failed, you can head over to NeverBounce to check the quality of your list and clean it. If you clean the list, you'll be able to upload it to Hive 👍