Go to Start > Copy and paste the following command line in the ‘Search programs and files’ box and Press Enter.

Outlook /safe

If Outlook safe works as expected, disable the add-ins as suggested below:
a. Click on File menu.
b. Click Options.
c. Click Add-ins.
d. Click on Go button besides Manage: Com-Add-in.
e. Check if there are add-ins listed, clear the checkbox to disable them.
f. Close the Outlook and restart it.

https://answers.microsoft.com/en-us/outlook_com/forum/all/outlook-2010-wont-open-wordexcel-attachments-they/f6e8cf7f-9349-4ebd-9c77-122b05f3e1b0