Environment: Windows 10, Office 2016 x64
EV client version: 10.0.4.1189
EV Server version: 10.5
Enterprise vault appears to be functioning on some level because users can still get to archived emails, however no attachments can be accessed. In addition, users have reported that the Enterprise vault tab is no longer visible within Outlook. This only seems to effect those machines that have Windows 10 and Office 2016, user who are on Windows 7 and Office 2013/2010 have not reported any issues.
I have told you all of this because I wanted to verify what is in the compatability chart: Is the version of Enterprise vault described at the top of this post compatible with Office 2016 x64 on a Windows 10 system? If not, what version do we need to upgrade to? Thanks.
Three compatibility problems based on your post.
1) There is no such release as "EV Server version: 10.5." The latest update to the EV 10 product is version 10.0.4.1354, also known as "10.0.4 CHF3."
2) Support for Windows 10 as a client operating system for the EV Outlook Add-in (client) requires at minimum EV Outlook Add-in version 11.0.1 CHF3. Depending on how updated your Windows 10 is (Anniversary Update, Creators Update, Fall Creators Update, etc.) you may need a later version still. See this chart and its footnotes for the details.
3) Support for Outlook 2016 with the EV Outlook Add-in (client) requires at minimum EV Outlook Add-in version 11.0.1 CHF4 and EV Server 11.0.1 CHF4. See this chart and its footnotes for the details.
Short answer to your question is that you need to upgrade both your EV server and client to at least 11.0.1 CHF4 to support your combination of Windows and Outlook versions.