[Koha] Outstanding order (only one order per subscription is allowed)

Hi I am having a problem entering serials information in the Acquisitions module. I keep getting the message "Outstanding order (only one order per subscription is allowed)" when I try to enter a subscription into the new basket for the vendor. I don't really understand the relationship between renewing a subscription in the Serials module and entering budget information in the Acquisitions Module. Can anyone direct me to more information than is in the Manual. I am using 3.20.4 Thanks Ann Ann Murphy Librarian Katikati College Beach Road, Katikati, 3129 New Zealand 0064 7 5490434 amurphy@katikaticollege.school.nz