This issue may be caused by the Autodiscover-related registry data:
HKEY_CURRENT_USER\Software\Microsoft\Office\x.0\Outlook\AutoDiscover
Review the following possible DWORD values that may be located under the \Autodiscover subkey.
• PreferLocalXML
• ExcludeHttpRedirect
• ExcludeHttpsAutoDiscoverDomain
• ExcludeHttpsRootDomain
• ExcludeScpLookup
• ExcludeSrvRecord
• ExcludeLastKnownGoodURL (only applies to Outlook 2010 version 14.0.7140.5001 and later versions)
• ExcludeExplicitO365Endpoint (only applies to Outlook 2016 version 16.0.6741.2017 and later versions)
If the issue persist, you could test and solve Outlook problems with SARA
Support and Recovery Assistant is a new tool that helps users troubleshoot and fix issues with various Office 365 apps and services. The app diagnoses common Outlook issues like account setup, connectivity issues, password issues, or Outlook stops responding or crashes.
https://support.office.com/en-us/article/about-the-microsoft-support-and-recovery-assistant-e90bb691-c2a7-4697-a94f-88836856c72f?ui=en-US&rs=en-US&ad=US#/?env=ExRCA
https://social.technet.microsoft.com/Forums/Azure/en-US/9e2671d9-8de3-4965-b0fc-e210b7a33cd1/alternative-to-quotexcludescplookupquot-after-migration-to-office-365-for-business?forum=exchangesvrgenerallegacy