The issue of the 'No.' auto generated when use Custom API on an exist entity, it fails on Transfer Order custom API

Since there is no exist API for Transfer Order until now, I created my custom API to Save and Retrieve Transfer Orders, While retrieve/Get is working fine, I can not Post a new record as a Transfer header, The error I am getting is:

"error": {
"code": "Internal_RecordNotFound",
"message": "The Transfer Header does not exist. Identification fields and values: No.='' CorrelationId: 13c5d54d-61da-4667-a6b3-fd79b9ef6d58."

I do not provide the ‘No.’ field, because If I did I will receive this:


You may not enter numbers manually. If you want to enter numbers manually, please activate Manual Nos. in No. Series T-ORD.


(And I should not do activate the manual No. process.)

I am not able to insert any new Transfer Header record.

Any idea or help much appreciated