PushRawTx android error.

[EnettyTech]

let request = await fetch('https://api.cryptoapis.io/v1/bc/btc/testnet/txs/send/"', {
method: 'POST',
headers: {
'Content-Type': 'application/json',
'X-API-Key': 'xxxx'
},
body: JSON.stringify({"hex":tx})
});
let data = await request.json();
return data``
I try send transaction, ios working, but on android return error unexpected end of json.
Check status code: 308