Let’s Encrypt needs to validate that the domain points to the server trying to obtain the certificate – if this validation step fails repeatedly, it will trigger a 429 error.
Thankfully, there are some simple steps you can take to avoid this:
- Ensure that your domain name is resolving correctly to your server.
- If you recently made changes to your nameservers and/or DNS entries, these changes might not have yet propagated.
- To verify that the DNS entry for your domain has propagated correctly, you can use a free service such as DNSMap.
- If your domain is not resolving to your server’s IP or hostname, you should double-check your DNS entries.
- If you are trying to obtain a certificate for a sub-domain, ensure that it is set-up correctly.
- Finally, and this goes without saying: make sure you understand what’s going on before blinding making many tentatives.