Outlook 2016 Online Pictures won't import
MS made a change sometime in early Feb 2017 that broke the way Outlook uses Online Pictures.
I haven't (and probably won't) dig into what caused it to become broken, but the fix is:
Open IE, Gear Icon > Settings
Click the advanced tab, scroll down to Do not save encrypted pages to disk and uncheck it.
Click OK on the bottom, close IE, and try to use Online Pictures again.
This can also be pushed out via GPO.