Two methods are available for office repair; Quick and Online. 

• Quick repair will handle 90% of all issues and as the name says is faster (10-20 min)
• Online will download and "Reinstall" office and will handle 99.99% of all issues but can take much longer depending on factors like your bandwidth but is usually finished in under an hour

To start the repair

1. Open up the Control Panel on your PC (and show All Control Panel items, if necessary) and click on Uninstall a program
2. 
3. Right-click on "Microsoft Office 365" or "Microsoft 365 apps for Enterprise"
4. 
5. Click Change.
6. Select Quick Repair Or Online and Repair then follow the prompts. (see example dialog below)