Issue "The incoming quality certificate could not be stored" in QCERT idoc

Hi Experts,

We are getting the QCERT idoc from external system for purchase order , and when tried to post it gives the message "The incoming quality certificate could not be stored " and the idoc status changes to 52. Please let me know if u have encountered this issue , and had provided any sort of solution to this issue.

Regards,

Mahendra Kumar.