Please fill out the fields below so we can help you better. Note: you must provide your domain name to get help. Domain names for issued certificates are all made public in Certificate Transparency logs (e.g. https://crt.sh/?q=example.com), so withholding your domain name here does not increase secrecy, but only makes it harder for us to provide help.
It produced this output:
Detail: The key authorization file from the server did not match this challenge [tw4S15l3HaHGYVETV4T8DXZKrHMWiCZYj9JAwBA2tmI._FbOP2J5b0VWu0eF0q2-QvEMz3PGY7WIhFN3TvucLrc] != 
My web server is (include version): Apache
The operating system my web server runs on is (include version): Linux
My hosting provider, if applicable, is: all-inkl.com
I can login to a root shell on my machine (yes or no, or I don’t know): no
I’m using a control panel to manage my site (no, or provide the name and version of the control panel): yes, name unknown
today I tried to generate a new certificate like described above. I used a virtual machine of Fedora 28, the certificate is for a webhosting package.
I have done this multiple times in the past with other domains successfully.
This time I tried many many variations and options and no success. Everytime certbot tells me that the challenges are not accessible. Its not true. I can access the uploaded challenges via webbrowser with no error page…
The challenges are correctly generated with the correct file name and content.
I found via Google many discussions about the problem with IPv4 domains with no working IPv6. This is the case here. In the DNS (not editable for me!) is not configured any IPv6 record. Also tests with some test sites are unsuccessful (http://ipv6-test.com/validate.php).
I can also NOT configure at this site DNS TXT records for DNS challenge.
I tried also https://zerossl.com/ with the same error result.
I used certbot 0.26, today updated via dnf upgrade.
So, what can I do to have a Letsencrypt certificate for this IPv4 only domains?
Any help would be highly appreciated.