Error when deploying ARM template that includes certificate stored in key vault
I think I found the cause of this issue. Apparently, when a resource group has been created, you cannot change the secret name. If you do so, the error above will be thrown.
If you want to change the secret name, you need to delete the resource group and redeploy everything.
Have you been changing the secret name in the ARM template, without removing the full resource group in the azure portal?