Hi John,
Regarding the description above, I'd like to confirm the following things:
1. Have you just found the issue? Did the Blog site work before?
2. Have you deployed ADFS, DirSync?
3. Does the issue occur to other users, except you and your boss?
4. Are the affected users synced from local AD or created in your Office 365 admin center?
5. Is your Office 365 upgraded from Office 365 pre-upgrade, or you're always using the new version of Office 365?
Before getting your feedback, you can refer to the following steps to narrow down the issue from your side:
1. Check to see if you can access the Site settings page of your blog site via <Copy the URL from the error page>/_layouts/15/settings.aspx. Just use “settings.aspx” to replace the “start.aspx”
2. On the error page, click GO BACK TO SITE to see if you go back to your own My Site.
3. Try clearing the cache data and cookies in your IE or change to another web browser, then see if the issue persists.
4. Go to your My Site or click SkyDrive or Sites in the top link bar, and click the gear in the upper right corner->Site contents->new subsite to create a new Blog site.
5. Check to see if the issue influences all of the users in your organization.
Feel free to let me know any updates, and I’ll try my utmost to help with the issue.
Thanks,
Cherry