Hi Pablo, follow these steps to perform a full repair of your Office installation . . .
Open Control Panel - Programs and Features
Click Microsoft Office in the list of installed applications
At the top, click 'Change'
On the resulting dialog, click 'Repair' - try the Quick Repair first and check to see if this is resolved, if not, choose the Online Repair, it is a comprehensive fix
That will take a while, but should fix any issues with your Office Installation . . .
NOTE: Please be advised, if you are running Office 2013 or earlier, before attempting a repair, have your Microsoft Office Product Key at hand, Office may need to be re-activated in some cases