The ASCII code of the 1. parameter name is not in ascending order, or the generated MD5 string is not converted from uppercase to lowercase. The solution to this problem is simple. Just check it on WeChat official website with the checking tool.

2. Wrong key. Pay special attention here, the key of the public platform and the key of the merchant number are different! ! ! After the approval of WeChat payment is successful, you will receive an email with appid merchant number, merchant background login number and password, log in to the merchant background: account settings-security settings-switch to api security, download the certificate, there is an API key below, fill in a string, save, and use this manual setting for the last two signatures.

Finally, I remind you that you must read the emails and documents carefully in the future.