Users have reported that during the upgrade to 2.4.4 from previous versions of 2.4, they recieve the message 'Failed To Upgrade Configuration File'
This does not seem specific to 2.4.4, as there were some reports during 2.4.3.
It seems to occur when a user has moved their old copy to a backup folder. They then upload the new files to their active foldername, and copy their config files (default.conf.php and www.example.com.conf.php) to the new installation's var folder. Perhaps this assists in testing, but it is not guarenteed all users took this step, or that it is part of the cause.
The upgrader will pass the System Check page - and full write permissions are granted to the 'var' folder.
1 user reported that deleting the 'default.conf.php' helped them solve this error message, however it didn't seem this fix helped other users.
It seems to happen during the part of Upgrade which creates a backup of the configuration file, and then tries to overwrite the current config file.
This might be related to the issue of ticket