code 46 unsupported media type

Salve,
potreste darmi una indicazione sul significato del codice di errore:

{"code":46,"message":"Unsupported media type","wlt":"3PphCsbA"}

Sotto riporto la richiesta di autenticazione.
Grazie e cordiali saluti

curl --request POST
--url 'https://staging.authservices.satispay.com/wally-services/protocol/tests/signature'
--header 'host: staging.authservices.satispay.com'
--header 'date: Wen, 16 Dec 2020 18:24:05 +0000'
--header 'digest: SHA-256=RCtf9dVtFQlDmKB2lBPSibcYiQHIcLJWsKjWG9HQvnU='
--header 'Authorization: Signature keyId="o6s6g9qcfkc5fmiud97himsb45g9fc1oj80nnfnod0fu1opq7525jd5d2net4gm4ppro71bjjedj18d2653p778efppg8d2rici61b53sfup1kovlbst7spaldo5dc8nkck1u7o18ta6ikahl4nvrlimhbsjjj07kg1skls8c1qsf8r26a9ue3922a786jlfav6pd6n5", algorithm="rsa-sha256", headers="(request-target) host date digest", signature="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"'
--data '{"flow":"MATCH_CODE","amount":"89999100","currency":"EUR","external_code":"my_order_id","callback_url":"http://localhost:56993/checkout.aspx","metadata":{"order_id":"my_order_id","user":"my_user_id","payment_id":"my_payment","session_id":"my_session","key":"value"}}'