Trouble with OpenSea API v2: 'Invalid signature' error when listing NFT on Polygon

NFT
1

Hey folks, I’m stuck with a problem using OpenSea’s API v2. I’m trying to list an NFT on the Polygon network, but I keep getting an ‘invalid signature’ error. I’ve got my API key and it works fine for other API calls.

I’ve tried different ways to get the signature, including web3.js and ethers.js, but no luck. Now I’m using Seaport for the signature, but it’s still not working.

Here’s a simplified version of what I’m doing:

const signAndList = async () => {
  const provider = new ethers.providers.JsonRpcProvider('polygon_rpc_url');
  const signer = new ethers.Wallet('my_private_key', provider);
  const seaport = new Seaport(signer);
  
  const orderParams = {
    offerer: 'my_wallet_address',
    offer: [{ /* NFT details */ }],
    consideration: [{ /* Payment details */ }],
    // Other required params...
  };

  const signature = await seaport.signOrder(orderParams);
  
  const listingData = {
    parameters: orderParams,
    signature: signature
  };

  // Attempt to list using OpenSea API
  const response = await axios.post('opensea_listing_endpoint', listingData, {
    headers: { 'X-API-KEY': 'my_opensea_api_key' }
  });

  console.log(response.data);
};

signAndList();

Any ideas what I might be doing wrong? Has anyone successfully listed on Polygon using the v2 API? Thanks for any help!

2

hey hugo, i’ve been playin around with opensea’s v2 api lately and ran into some hiccups too. have you tried double-checking your wallet balance on polygon? sometimes low MATIC can cause weird errors. also, make sure you’re using the latest seaport version - they update it pretty often.

another thing to consider - are you setting the right expiration time for your listing? i’ve seen cases where a too-short or too-long expiration can cause signature issues.

oh, and here’s a random thought - have you tried using a different rpc endpoint? sometimes the public ones can be finicky.

what kind of nft are you trying to list, btw? some collections have special requirements. maybe we can brainstorm more if we know what you’re working with. keep us posted on how it goes!

3

I encountered a similar issue when working with OpenSea’s API v2 for Polygon listings. One often overlooked aspect is the gas fees. Ensure you’re accounting for the gas price and gas limit in your transaction parameters. Additionally, double-check that your Seaport instance is configured correctly for the Polygon network. It might be worth verifying the NFT’s contract address and token ID are accurate as well. If the problem persists, consider using OpenSea’s SDK instead of direct API calls, as it can handle some of these intricacies automatically. Lastly, make sure your API key has the necessary permissions for listing operations on Polygon.

4

hey mate, i’ve seen this error too. try checkin’ ur nft details, sometimes small typos mess the signature. also, confirm ur polygon chain id is 137. if still no luck, log full orderParams to catch any odd values.