In which line exactly are you seeing this error?
What firmware do you have running on your device when you do this?
Can you please attach the descriptor table file of your firmware (dscr.a51) here?
Can you please answer my other questions.
All your endpoints are IN endpoints. As per your descriptor and host application your target endpoint is EP8.
If all your endpoints are IN endpoints, from where and how are you sourcing the packet?
Does EP8 have a packet when you trigger the transfer, what is the size of the packet?