Sorry we have trouble starting Outlook

Copper Contributor



Since the latest version of Office 365 there is an error shown when you open a second Outlook instance.


"Sorry we have trouble starting Outlook. Only one version of Outlook can run at a time. Check to see if another version of Outlook is running or try restarting your computer."


´This problem only occurs with the latest version 1806 (10228.20080)

It's easy to reproduce:


Start Outlook once

In the taskbar right click the icon of the running Outlook instance and try to start a second instance.

Then this error occurs, after clicking the "Ok" button the second instance starts.


This build of Outlook has so many annoying bugs (this one, Calendar permission, Skype for Business Addin German template)



Reinhard Schuerer

nascom GmbH


3 Replies

This is a known issue that has been reported.  The cause is the change to a five digit build number which broke a function that assumed four digit build numbers.  I have no ETA on the fix, but it's coming.

Was there a resolution to this?  The issued just started on my computer.  @Hal Hostetler 

@Reinhard Schuerer 


When you click on the Outlook icon to launch Outlook, you are presented with the above error, and Outlook fails to open.

  1. Click on the Outlook icon in your Taskbar, to trigger the Outlook error.
  2. With the error open (Don’t click on OK) Right-click on the NEW Outlook icon (should be on the far-right of your icons in the Taskbar), and click on “Pin this program to taskbar”.
  3. Now Right-click on the old Outlook icon (somewhere to the left of your new icon) and click “Unpin this program from taskbar”.
  4. This removes the old shortcut, that triggered the error and caused Outlook to crash.  The error may still pop up after this, but Outlook should now open after you click OK.
  5. If you would like your icon back where you’re used to it being, simply click and drag the icon in the Taskbar, to its new location and release your click when you want to drop it in its place.




Office 365 migration expert