Something has changed for storage in new regions (e.g. UK South) so this check no longer works, it might be that upgrading the WindowsAzure.Storage package would also solve it but switching to CreateIfNotExists does the job

Jeavon · Jeavon · commit a8c17ffa19fc · 2016-09-20T17:37:30.000+01:00
diff --git a/src/UmbracoFileSystemProviders.Azure.Installer/InstallerController.cs b/src/UmbracoFileSystemProviders.Azure.Installer/InstallerController.cs
@@ -457,7 +457,7 @@ private static bool TestAzureCredentials(string connectionString, string contain
                 CloudBlobContainer blobContainer = cloudBlobClient.GetContainerReference(containerName);
 
                 // This should fully check that the connection works.
-                return blobContainer.Exists();
+                return blobContainer.CreateIfNotExists();
             }
             catch (Exception e)
             {

Original file line number	Diff line number	Diff line change
`@@ -457,7 +457,7 @@ private static bool TestAzureCredentials(string connectionString, string contain`
`457`	`457`	`CloudBlobContainer blobContainer = cloudBlobClient.GetContainerReference(containerName);`
`458`	`458`
`459`	`459`	`// This should fully check that the connection works.`
`460`		`- return blobContainer.Exists();`
	`460`	`+ return blobContainer.CreateIfNotExists();`
`461`	`461`	`}`
`462`	`462`	`catch (Exception e)`
`463`	`463`	`{`