Hi Ihab,
To clarify the situation, I’d like to confirm the following points:
1. Did the Office installation complete without any errors?
2. Do you have any other version of Office installed on the computer?
This issue may occur if the Office 365 Proplus installation is corrupted.
You can try repairing Office 365 Proplus from the Control Panel and see if that helps. More information can be found here:
http://office.microsoft.com/en-us/project-help/repair-or-remove-office-HA010357402.aspx
If the issue persists after you try the steps above, we need to remove all traces of the Office installation by running the fix it from the following article:
http://support.microsoft.com/kb/2739501
Then re-install Office 365 applications.
Please let me know if this answered your question.
Thanks
Jeremy Ren