Chrome Extension APIs

I’m building an extension for myself, so I can add Ethereum or BNB wallets and see their balances. But when I put the wallet and press “Add”, I get errors that I don’t know how to solve anymore.

Extension

At first I was getting an API error, then I don’t get any more, but now I get these two errors:

Console Error

I leave the complete JSON:

const walletForm = document.getElementById("walletForm");
    const walletAddress = document.getElementById("walletAddress");
    const totalBalance = document.getElementById("totalBalance");
    const walletList = document.getElementById("walletList");
    
    walletForm.addEventListener("submit", (e) => {
      e.preventDefault();
      const address = walletAddress.value.trim();
    
      if (address) {
        addWallet(address);
      }
    
      walletAddress.value = "";
    });
    
    const ETHERSCAN_API_KEY = "FAKEAPI";
    const BSCSCAN_API_KEY = "FAKEAPI";
    
    async function addWallet(address) {
      try {
        const ethereumBalance = await getEthereumBalance(address);
        const bnbBalance = await getBNBBalance(address);
        // Resto del código para agregar la billetera
      } catch (error) {
        console.error(`Error en la función addWallet: ${error.message}`);
      }
    }
    
    async function getEthereumBalance(address) {
      try {
        const response = await fetch(`https://api.etherscan.io/api?module=account&action=balance&address=${address}&tag=latest&apikey=FAKEAPI`);
        if (!response.ok) {
          throw new Error(`Error en la respuesta de la API: ${response.statusText}`);
        }
        const data = await response.json();
        if (data.message === 'OK') {
          console.log(`Resultado de la llamada de API: ${data.result}`);
          return BigInt(data.result);
        } else {
          throw new Error(`Error en la respuesta de la API: ${data.message}`);
        }
      } catch (error) {
        console.error(`Error en la función getEthereumBalance: ${error.message}`);
        return null;
      }
    }
    
    async function getBNBBalance(address) {
      try {
        const response = await fetch(`https://api.bscscan.com/api?module=account&action=balance&address=${address}&tag=latest&apikey=D96DAB88GRZY5UZ3YFJSZMUVA6E5H8EMU8`);
        if (!response.ok) {
          throw new Error(`Error en la respuesta de la API: ${response.statusText}`);
        }
        const data = await response.json();
        if (data.message === 'OK') {
          console.log(`Resultado de la llamada de API: ${data.result}`);
          return BigInt(data.result);
        } else {
          throw new Error(`Error en la respuesta de la API: ${data.message}`);
        }
      } catch (error) {
        console.error(`Error en la función getBNBBalance: ${error.message}`);
        return null;
      }
    }

Its just an extension, why is so hard? I feel the problem in the API code, but.. I dont knok.