I read many posts about this Error: LetsEncrypt challenge request 429 and couldn’t find any solution.
I bought this domain on 1and1 now it’s merged with IONOS. The problem was a simple one. All you need to do is go to your domain control panel and delete AAA record that points to IPv6 address to 1and1 server.
Just make sure all whats left are your A type records that point to your IPv4 address.
My domain is: enzymaticcleaner.co.uk