I've never seen the database file error.
The way the workflow work is by searching through Spotlight for filetypes belonging to Outlook (contacts, messages and events) in the ~/Library/Group Containers/UBF8T346G9.Office/Outlook/Outlook 15 Profiles/Main Profile folder.
It could be:
Some sort of permission issue (check that the ~/Library/Group Containers/UBF8T346G9.Office/Outlook/Outlook 15 Profiles/Main Profile folder is readable)
A path issue (lets say, your database had to be renamed because of a corruption, do you have more than one profile folder in ~/Library/Group Containers/UBF8T346G9.Office/Outlook/Outlook 15 Profiles/?)
A launch service database issue (you need to rebuild the launch service database, a free app like Onyx could do that for you).
Corentin
