Neil McDonald's Dynamics 365 Blog

After your Dynamics 365 organisation has finally been updated to the July 2017 October 2017 December 2017 February 2018 V9 version, you may find that your Outlook client (full version, not the lightweight app) no longer works.

Uninstalling and re-installing the version offered via the  ‘Get Apps’ page within Dynamics 365 doesn’t help as you are repeatedly prompted for your login when trying to configure the organisation.

Viewing the trace log gave the error:

Metadata contains a reference that cannot be resolved: 'https://crm_url/XRMServices/2011/Organization.svc?wsdl&sdkversion=8.2

This is because the Outlook client is still using the old SDK (8.2)  which is still using SSL rather than the TLS1.2 protocol for authentication required by V9.

The solution is to install update KB4054414 after installing the Outlook client.