Hi Alexccarpentry,
Do you mean that you can't open the SharePoint website in IE? If yes, which Office 365 Plan are you using?
If you use Office 365 Plan P, have you changed the Name Server to Office 365?
If the Name Server has already pointed to Office 365, I suggest you double check the configuration of SharePoint Online public-facing website referring to the link below:
http://onlinehelp.microsoft.com/en-us/office365-smallbusinesses/gg549209.aspx
If you use Office 365 Plan E, please refer to the following link to set up SharePoint Online public website:
http://onlinehelp.microsoft.com/en-us/office365-enterprises/gg570301.aspx
If the issue persists, please capture some screenshots of "Manage DNS" in Office 365 for further troubleshooting.
Thanks,
Edward Qu