Hi @Paul Griffiths ,
Welcome to our forum.
It tells me that "cannot start Microsoft Outlook. Cannot open the Outlook window. The set of folders cannot be opened. The information store cannot be opened"
Did this issue occur when you first open Outlook 365 client? Or it occurr only recently and you could work normally before?
As I know, for the issue itself, in order to avoid the interference of add-ins, it's suggested to restart your outlook in safe mode and disable your add-ins to check(Windows + R>type"Outlook.exe /safe"> enter).
If the issue occurred only recently, have you performed any specific operations before it? Based on my research, the issue may also occur when your Outlook profile is corrupted, please try to create a new Outlook profile and re-add your account to test(Control Panel>Mail>Show profiles>Add>type a new profile name>readd your account)
Also, if it actually occurred when your first open Outlook client, it's suggested to repair your Outlook with SaRA tool, which could repair some general issues on your Outlook 365 client.
Hope that would be helpful to you. If your issue has any update, please feel free to post back.
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