Fixing Opening Documents in SharePoint. Here’s the answer from Microsoft for 2010, 2013 using Windows 10:
If you don’t want to use it, then here is how to go to the Trust Center:
- Click File, then Options
- Once the Options Menu appears choose Trust Center
- The Trust Center area appears. Click on Trust Center Settings
- Click on Trusted Locations on the left. If the location of your SharePoint is not showing, add it by clicking Add new location