Hi Shareef,
The error because of the Account used while creating the PO thus the error. I believe this error is being thrown from ERP system for the Account which might got deactivated there. Kindly check the Account used in PO and check in ERP if same has been deactivated. If so, either you can get the Account activated again in ERP or can change the same in PO to something else.
Sandeep Jain