Hi Paul,

It appears you've got the Storage key and its values set as Umbraco:CMS:Storage, not Umbraco:Storage. Also as a sidenote it also appears you've got an extra CMS key in the chain with Umbraco:CMS:CMS:Hosting.

Here's the corrected JSON based on your posted example:

{
   "Umbraco":{
      "CMS":{
         "Global":{
            "Id":"MYID",
            "SanitizeTinyMce":true
         },
         "Content":{
            "AllowEditInvariantFromNonDefault":true,
            "ContentVersionCleanupPolicy":{
               "EnableCleanup":true
            }
         },
         "Hosting":{
            "Debug":false
         }
      },
      "Storage":{
         "AzureBlob":{
            "Media":{
               "ConnectionString":"DefaultEndpointsProtocol=https;AccountName=<STORAGENAME>;AccountKey=<MYKEY>;EndpointSuffix=core.windows.net",
               "ContainerName":"<CONTAINERNAME>"
            }
         }
      }
   }
}

Hopefully that resolves your issue. I've recently got this working with the latest version of Umbraco too, so all being well that'll clear the missing ContaininerName error you're getting.

All the best,

Andy.