There are a number of reasons why a message or service instance may enter the Suspended Non-Resumable state – can you provide details of the error and we can provide some further help.
The error details can be found under the Service Details dialog, Error Information tab for a Suspended Non-Resumable message or service.
It really does depend on your solution, however it is normally caused by non-recoverable failures, such as unhandled exceptions, or failures sending messages etc.