Recently I had a problem with OneDrive for business and my Sync’d files. Every time I went to open one of the documents Office applications would just crash and said it had a problem with protected mode. The error presented after word kind of crashed was:
Off I went to the settings in word and found the following, go to File > Options > Trust Center > Trust Center Settings > Privacy View and uncheck the top two options.
Now I can open Office documents from OneDrive without any errors. Oh, close the apps and reopen then first!
You can also configure this by group policy for your entire environment go to the Office 2013/2016 ADMX template in Group Policy Management and navigate to:
User Configuration > Policies > Administrative Templates > Microsoft Office 2013 > Security Settings > Trust Centerfa