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I'm sorry about the issue, If you do not find Office 365 installed on the computer, then you need to re-install it, You may login to the My Account page on Office.com with the Microsoft account you used to register or subscribe to and then download and install Office 365.
You can download Internet explorer again from : https://www.microsoft.com/en-us/download/internet-explorer-11-for-windows-7-details.aspx
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