Hi JoshuaMaurici , in version 2022.8, MYOB have altered the rules around posting data, see the article below. This change will require some 3rd party addons to change their interaction with the MYOB API. You should forward this link to Maropost support.
https://apisupport.myob.com/hc/en-us/articles/5319928281871-Changes-to-POST-requests
I am getting the same error on an insertex.
I don't understand what I have to do to change my code.
I running,
ServiceBillService serviceBillService = new ServiceBillService(mcfvm._configurationLocal, null, mcfvm.MyOAuthKeyService);
ServiceBill newServiceBill = serviceBillService.InsertEx(mcfvm.cf, serviceBill, mcfvm.credentials, ErrorLevel.WarningsAsErrors);
