ios – Apple in app purchase: The Token’s Signature resulted invalid when verified using the Algorithm: SHA256withECDSA

I am using this library from apple to verify a transaction made with Apple in-app purchase:
https://github.com/apple/app-store-server-library-java

I have a valid signed transaction, when I use the SignedDataVerifier, it throws
SignatureVerificationException: The Token's Signature resulted invalid when verified using the Algorithm: SHA256withECDSA

Here is my code:

fun verifyCertificate() {
        val bundleId = "my bundle id"
        val environment = Environment.SANDBOX
        val rootCAs = mutableSetOf(
            computerCert.inputStream,
            incCert.inputStream,
            g2cert.inputStream,
            g3cert.inputStream
        )

        val signedDataVerifier  = SignedDataVerifier(rootCAs, bundleId, null, environment, false)

        val signedTransaction = "eyJhbGci..."
        try {
            val transaction = signedDataVerifier .verifyAndDecodeTransaction(signedTransaction )
            println(transaction)
        } catch (e: VerificationException) {
            e.printStackTrace()
        }
    }