Anchor function does not work

Hello, I have a question while testing a free Adobe Sign developer account.
I wanted to automatically create a signature line as a form field in the contract, so I looked at the API document, set the json data, and sent it, but the signature line wasn't there.

This is one of the jsons data I sent the api request.

{"redirectOptions":[{"action":"DECLINED","url":"CONTENT FILTERED"}],"participantSetsInfo":[{"role":"SIGNER","name":"signer_1","memberInfos":[{"email":"emro.adobesign@emro.co.kr"}],"order":"1"},{"role":"SIGNER","name":"signer_2","memberInfos":[{"email":"hy.cho@emro.co.kr"}],"order":"2"}],"name":"test4","signatureType":"ESIGN","formFieldGenerators":[{"formFieldNamePrefix":"bp_signature","participantSetName":"signer_1","formFieldDescription":{"inputType":"SIGNATURE","required":true},"anchorTextInfo":{"anchorText":"Purchaser","anchoredFormFieldLocation":{"width":10,"height":10},"fileInfoLabel":"Document"}},{"formFieldNamePrefix":"sp_signature","participantSetName":"signer_2","formFieldDescription":{"inputType":"SIGNATURE","required":true},"anchorTextInfo":{"anchorText":"Supplier","anchoredFormFieldLocation":{"width":10,"height":10},"fileInfoLabel":"Document"}}],"fileInfos":[{"transientDocumentId":"CBSCTBABDUAAABACAABAAmIMuDNnAvVxXxek8xT4_PqQBdU2E5CJpShUydPQ3VIVAeBQaLztcFyBZ58f4fNBdCOZ0cYqUiLf9G4YtRE7LzclROx9ZTa2PayEmF6DMxgd8uAwuHa3WxqEJFeapkoeiTKMgpxMn-ZqZim7H5nlNXpHCzoRX-9fYeK4lNDLqo91PQ8-6IHHxygHBSZkmuWVb5x08liO552veQBgqK6ZH_GEnZ0Gw8c9VFN8XmQDZ4SEPUsnz5upuWBvass3LG7IxFB2tw__AV8XDz-MIDrHT1aQmAXWWDg_7W05ngDKiXLIHdpNV4cGOVLkDTEnma5w1PgHh5mN4JkL0oHoQLuaZo4yqYV7w5OahQDLVyUJwE2c*","label":"Document"}],"state":"AUTHORING","postSignOption":{"redirectUrl":"CONTENT FILTERED"}}

Please let me know why the signature field is not set automatically.