I am having same issue. This is what I have found after switching to new Outlook:
My main email account worked (standard). Another email account didn't work (Standard) - both previously in old Outlook
I added another of my exchange emails NOT previously in old Outlook, basic licence - It worked
I tried removing the other email account that was previously in old Outlook from accounts in system, then trying again - it still will not work. Other email accounts not associated with Microsoft work
To me it seems like it is not a basic vs standard licence issue. Maybe it is a glitch where accounts that are not the one associated with the desktop app that were in old Outlook are causing the issue. Any help would be appreciated.