New
#11
Hi Kari!
I searched the one error you showed in one of your snips the; X-OWA-Error: Microsoft.Exchange.Data.Directory.ADDriverstoreAccessNonlocalException . and came up with this, Unable to access Outlook.. Something went wrong :-(
Your problem could stem from a bad win10 update, and I am assuming that the machine that your having this problem is current.
It has a couple of suggestion you could try. You have said that you couldn't sign-in to that specific account that isn't working, but Maria ThePanda's answer calls for signing-in through one of your other working accounts to create the alias and then try to sign-in to the non-working account using the alias.
The other is BMense67 reply at the bottom of the page, you may already have an alias that is blocking your log-in.
Whatever this win10 update is, it seems like its messing with the synchronicity across outlook and O365 accounts. I would check all of your devices; Desktops, phones, laptop, bluetooth.