This could happen because of a delay between your initial sign in and Office 365 for business setting up your environment. If Office is taking a long time to install you may be on a slow connection or you another install or update may be happening in the background. See Office is taking check out this one from Bligblogging long to install or Office hangs at 90% for possible solutions. For example, you can't install Office on computers running Windows Vista or Windows XP, or on devices that aren'...