General issues, or "An error occurred. Please try again or contact our support"
To troubleshoot the problem, please reproduce the error and take a look into the WHMCS gateway log. The gateway log records all requests and responses made by the module, so it may contain useful information about the cause of the problem.
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Gateway log: "Binance headers missing. Ensure your server (or WAF, CDN, etc.) does not strip off HTTP headers"
The log entry means that the module did not find the necessary HTTP headers in the HTTP request. Either the callback file was manually accessed via the browser, or your server or a proxy in front of it removed the headers.
To solve the problem, the web server must be configured to pass all HTTP headers starting with "binancepay-" to PHP. With a default configuration, this is already the case, and many WHMCS payment gateways require custom HTTP headers to be processed in order to function properly.