Cloud Agent: Failed to list container's vhds blobs

Hi, I'm trying to run Team City's cloud agent feature on Azure as per this page https://confluence.jetbrains.com/display/TW/Microsoft+Azure+cloud. When I try to launch an agent I get the following error:

jetbrains.buildServer.clouds.CloudException: Failed to list container's vhds blobs: An error occurred while enumerating the result, check the original exception for details.jetbrains.buildServer.clouds.CloudException: Failed to list container's vhds blobs: An error occurred while enumerating the result, check the original exception for details.
at jetbrains.buildServer.clouds.azure.arm.connector.AzureApiConnectorImpl$getBlobsAsync$1.doResume(AzureApiConnectorImpl.kt:617)
at kotlin.coroutines.experimental.jvm.internal.CoroutineImpl.resume(CoroutineImpl.kt:54)
at kotlinx.coroutines.experimental.DispatchedContinuation$resume$1.run(CoroutineDispatcher.kt:152)

Is anyone able to tell me what might be wrong? TeamCity has contributor access to the subscription and it know it can see the storage account as it correctly picks the cloud agent os as Linux.