This is usually caused by an Outlook Add-in / Plug-in that conflicts with the installation and causes it to not complete successfully. The /resetfolders command is a tried and tested method of resolving this issue.

Click the Windows Start Menu button
Type 'Outlook /resetfolders'
Hit Enter/Return to run
Outlook should restart successfully and initialise the Workbooks Outlook Connector

If the error persists raise an issue with Support - www.workbooks.com/support