Office documents do not open after upgrading to Windows 10

Office documents do not open

You may receive one of the following errors:

• Word experienced an error trying to open the file

• This Excel file is corrupt and cannot be opened

• The application was unable to start correctly, PowerPoint found a problem with the file or PowerPoint can’t this read.

This is happening because Microsoft Office is trying to open an Outlook attachment from untrusted locations in Protected Mode, and failing. In such cases it is not recommended to disable Protected View. Protected View help keep your computer secure & safe. Files from the Internet and from other potentially unsafe locations can contain viruses, worms, or other kinds of malware, which can harm your computer. To help protect your computer, files from these potentially unsafe locations are opened in Protected View.

If you receive such errors, KB3086786 suggests the following:
Open an elevated command prompt, type the following and hit Enter:

icacls "%programfiles%\Microsoft Office 15" /grant *S-1-15-2-1:(OI)(CI)RX

You will see a Successfully processed message.

See if you are now able to open Office documents. You should be able to.
If not, then you may want to Repair Office.