Getting the message "Sorry we're having trouble opening this item" when trying to open an item in Outlook? It could be due to a corrupt cache.
The recommended fix is to drop Outlook in favour of an open source alternative like Thunderbird,
but since users get used to certain applications this may not be beneficial, so instead
the cache for Outlook is stored in %localappdata%\Microsoft\Outlook\RoamCache.
Open this directory (Win+R and paste %localappdata%\Microsoft\Outlook\RoamCache),
and delete all the files contained therein.
Other things to try:
outlook.exe /cleanviewsoutlook.exe /resetnavpane