Send tx error

I follow this step to send the transaction on the testnet:
https://docs.pokt.network/js/guides/quickstart

But an error message was returned
{
“code”: “0”,
“message”: “{"codespace":"sdk","code":2,"message":"ERROR:\nCodespace: sdk\nCode: 2\nMessage: \"error decoding transaction: proto: illegal wireType 7\"\n"}”,
“session”: {},
“node_public_key”: “”
}
Who can help me? Thanks.

I don’t understand what this error message means