Is the same 1200 error when logging in to Office?
I suggest you open Windows Settings > Accounts > Access work or school. If there is a connection of OneDrive for business account, click it and click Disconnect.
Go to Windows Credential Manager > Windows Credential, remove the credentials of your account.
Besides, go to Registry Editor, navigate to Computer\HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Common\Identity\Identities
Remove all identities under the Identities registry entry.
(Serious problems might occur if you modify the registry incorrectly. Before you modify it, please remember to back up the registry for restoration in case problems occur.)
Then please resign your account in OneDrive and Office apps for a check.
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