Hi llmft,
To help resolve this issue, I want to collect the following information :
1.You mentioned that “I have successfully installed on two computers”, is your meaning that you add the same account on two computers successfully or add other accounts for different users in Outlook clients successfully?
2.Are there any other users who also cannot add the Office 365 account into Outlook client in your company?
3.Did you delete the account that cannot been added in Outlook 2010 in Office 365 before and recreate it again?
Additionally, please refer to the link below to troubleshoot the issue :
Outlook cannot configure a new profile by using Exchange Autodiscover for an Exchange Online mailbox in Office 365:
http://support.microsoft.com/kb/2404385
Thanks,
Linda Wang