Hi EyeOnTech,
Generally speaking, a regular user who has the Office 365 ProPlus license is able to install Office 2011 for Mac and activate it with his user account. Given the situation, I suggest you check the user license to make sure he has the proper permission.
1. Log into the Office 365 Portal with your admin account.
2. On the User Management page, click on the user name and navigate to his licenses page. Check to see if the Office Professional Plus license has been checked. If so, I’ll suggest you remove this license for several hours, and then re-assign this license for him. It can refresh the license data from the server.
3. After doing this, please refer to this instruction to install Office 2011 for Mac: Install Office on your Mac with Office 365. If you get stuck while performing any the steps presented in the article, please offer the details for further troubleshooting.
If the issue persists, I’d like to collect more information for research.
1. Where did you download the Office 2011 for Mac?
2. Could you provide the screenshot about the error message?
Thanks,
Maggie Li