The download server for firmware and language files is not working if only HTTP is used.
Using HTTPS seems to work.
curl -v "http://downloads.snom.com:80/config/gui_lang_10.1.54.13.xml"* Trying 188.40.44.83:80...* Connected to downloads.snom.com (188.40.44.83) port 80 (#0)> GET /config/gui_lang_10.1.54.13.xml HTTP/1.1> Host: downloads.snom.com> User-Agent: curl/7.84.0> Accept: */*>* Mark bundle as not supporting multiuse< HTTP/1.1 500 Internal Server Error< Date: Fri, 09 Dec 2022 11:07:56 GMT< Server: Apache/2.2.22< Vary: Accept-Encoding< Content-Length: 539< Connection: close< Content-Type: text/html; charset=iso-8859-1<<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN"><html><head><title>500 Internal Server Error</title></head><body><h1>Internal Server Error</h1><p>The server encountered an internal error ormisconfiguration and was unable to completeyour request.</p><p>Please contact the server administrator, webmaster@localhost and inform them of the time the error occurred,and anything you might have done that may havecaused the error.</p><p>More information about this error may be availablein the server error log.</p></body></html>* Closing connection 0