Impossible to make it work

[PHPCreed]

I'm following the sdk but it's impossible for me to make the software work.

Im using this code:

   const priceRoute = await paraSwapMin.swap.getRate({
        srcToken: USDT,
        destToken: CAKE,
        amount: srcAmount,
        userAddress: wallet.address,
        side: SwapSide.SELL,
        options: {
            otherExchangePrices: true,
        }
    });

    console.log(priceRoute)

    const { bestRoute, others } = priceRoute;
    const swapExchange = bestRoute[0]?.swaps[0]?.swapExchanges[0];
    console.log("Swap Exchange: " + swapExchange.exchange)
    console.log("GAS USD: " + swapExchange.data.gasUSD)


    const destAmountFixed = new BigNumber(priceRoute.destAmount).times(0.99).toFixed(0); //get a little lower.
    const txParams = await paraSwapMin.swap.buildTx(
        {
            USDT,
            CAKE,
            srcAmount,
            destAmountFixed,
            priceRoute,
            userAddress: wallet.address,
            partner: 'sdk-test',
        }
    );

    const transaction = {
        ...txParams,
        gasPrice: '0x' + new BigNumber(txParams.gasPrice).toString(16),
        gasLimit: '0x' + new BigNumber(5000000).toString(16),
        value: '0x' + new BigNumber(txParams.value).toString(16),
    };

const txResponse = await wallet.sendTransaction(transaction);
    console.log(txResponse)
    const receipt = await txResponse.wait()

and although it's exact like the manual (and the test) i get data: { error: 'Validation failed: "srcToken" is required' }
I tried to add the key names as well, and it bypasses this error but then later i get

reason: 'chainId address mismatch',
code: 'INVALID_ARGUMENT',
argument: 'transaction',

Don't know what is the problem.