You may be experiencing some new issues while attempting to open attachments in Outlook. This is due to an Outlook security update applied to Outlook 2007, 2010, 2013, 2016+ in a June 2017 package.
Microsoft’s answer at this time is for you to right-click the attachment,save to desktop, then open the attachment. This IS a far more secure way to handle the attachment giving your virus/malware protection an opportunity to scan the file upon the copy instead of trying to catch a problem upon opening which often fails.
However, if you are having issues with this “feature”, please let us know and we can help address it in your organization or individual computer.