The merchant ID is invalid. Please try again.

I am using the api
to generate a payment for binance I am testing how payments are generated

It also tries to decode the response that appears in the whebhook, but it sends an error in the api to obtain the public key

resulted in a 400 Bad Request response:
{"status":"FAIL","code":"400100","errorMessage":"Mandatory parameter ‘Nonce’ was not sent, was empty/null, or malformed. (truncated…)

I would suggest you to reach out the binance pay team: Crypto Merchant Support & FAQ | Binance Pay Merchant