i got similar issue, it report :
LogWmfMedia: Error: Failed to resolve URL https://dnnrz1gqa.blob.core.windows.net/portals/attachments/Engine/MediaFramework/HowTo/StreamMediaSource/Infiltrator%20Demo.mp4?sr=b&si=DNNFileManagerPolicy&sig=F%2BBpnYueeQTUTSW0nCRSrXEfr35LIawe7C3MQoe2%2FPI%3D: 0x80072efd