not able to cancle the Invoice MR8M

Hi

User is try to cancel the Invoice .But he is not able to
cancel .System throwing error is “Invoice
document can’t cancelled” but when I checked in HELP button it is telling -this is
not possible as the document has not yet been posted. Message No M8490 .But for this Accounting
document generated. When I check work flow for this it is showing still in process. Then
why system generate accounting document . Now user want to cancel the document. How to I suggest the user on this. Please suggest..

I have attached the relevant documents for clarification.

Please suggest

Thank you

Regards

Dharma