The error indicates that the message has made it thru the pipeline and has been published to the message box but cannot find a matching subscription. i.e. a send port or orchestration that will process the message. You need to check the subscriptions (use BTSSubscriptionViewer.exe) and match with the promoted properties.
What pipeline are you using?
If you have 2 schemas with the same MessageType (targetnamespace#rootnode) then you can specify the required schema in XML Disassembler pipeline component ( with BTS2004 you need to use a custom pipeline containing the Xml Disassembler)
Another option is to declare a single Envelope schema and debatch and forward the content of the envelope. You need to declare separate schemas for the content messages. I have not used SAP with Biztalk, so am not sure if this is possible