Microsoft Outlook (Version 2401 Build 16.0.17231.20194), which is the latest version currently available, includes an issue that prevents Outlook from retrieving data from ActiveSync servers. Microsoft is aware of the issue and has reported that it will be fixed in a future version of Outlook. More information on this issue can be found here: https://support.microsoft.com/en-us/topic/da2dc0dd-297e-48ba-b6d9-ab18f5d522fc
Currently, the only workarounds are to downgrade to the previous version of Outlook (Version 2312 Build 16.0.17126.20132) or use a different mail protocol to connect to the server, such as IMAP or MDaemon Connector, or switch to a different mail client, such as MDaemon Webmail or eM Client.
Instruction for downgrading Outlook can be found in the following article: https://support.microsoft.com/en-us/topic/how-to-revert-to-an-earlier-version-of-office-2bd5c457-a917-d57e-35a1-f709e3dda841
We will post additional updates on our blog as we receive them.