The first place to start looking when your DKIM will not authenticate is your CNAME records. When entering GlassHive's CNAME records into your hosting site there is the possibility that characters will get lost, mistyped, etc.. To learn how to setup your DKIM you can view the article here "Setting Up Your DKIM".
When entering your CNAME records into make sure the CNAME's provided to you by GlassHive match the record input into your hosting site.
If the CNAME's do match inside of GlassHive and your hosting site, the next thing to check would be the TTL value. The lower the TTL the faster the ability of the records to validate inside of GlassHive. We generally recommend you set a TTL of 600 seconds or 10 minutes for the records to populate the fastest.