Sometimes, the authz requests sending to LetsEncrypt may be bad. This leads to authz request hanging in the "pending" status; and causing the request sending to the LetsEncrypt to fail because of "rate-limit".
This quick CLI option enable the option to clear out the authz requests sending stuck on LetsEncrypt API.
cat /var/log/letsencrypt/* | ./clear-authz /path/to/private_key.json
After running the command above, you should be able to clear out the "pending" authz request using LetsEncrypt API