Manually verifying never succeeds due a malformed URL, the / is missing; if I add the / the link is fine:
https://bernhard.hensler.net.well-known/acme-challenge/HGqB38utTQJ9bSBDT3VTDTtBjUROD5N6859GaCiJpjE
https://bernhard.hensler.net/.well-known/acme-challenge/HGqB38utTQJ9bSBDT3VTDTtBjUROD5N6859GaCiJpjE
Is that an Apache server problem? I use the latest Firefox, Safari fails as well … macos High Sierra, Server version: Apache/2.4.27 (Unix).
Thanks
bernhard