After enabling one domain in DKIM , you get errors in the GUI when trying to enable the others

The operation couldn’t be performed because object ‘xxxxx.com’ couldn’t be found on ‘MEAP282A03DC001.AUSP282A003.PROD.OUTLOOK.COM’.

This seems to happen once you create a DKIM for one domain and try and enable it on another straight after , Refresh the Browser Window

In Powershell:

Cannot enable DKIM for domains PS C:\Users\XXXX] New-DkimSigningConfig -DomainName XXXX -Enabled $false ConvertFrom-Json : Invalid JSON primitive: . At C:\Users\pwell\AppData\Local\Temp\tmpEXO_vqbcjjka.cbo\tmpEXO_vqbcjjka.cbo.psm1:579 char:35 + … etailsToPSObject = ConvertFrom-Json $ErrorObject.ErrorDetails.Message + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + CategoryInfo : NotSpecified: (:) [ConvertFrom-Json], ArgumentException + FullyQualifiedErrorId : System.ArgumentException,Microsoft.PowerShell.Commands.ConvertFromJsonCommand

You need to log out of powershell and relogin and do this for each domain