Check from your browser if the following can be downloaded:
Although the folders in the path above are available for v2.4.1, 2.4.2, ... 2.4.6, they may contain outdated files and in the latest 2.4.6 folder path, the Languages are packed wrongly though some updated versions exist.
It is possible your local IP may be blocked by virtue of the server subscribing to some blacklist in your IP resides.
Which extension do you wish to install manually? Just extract the contents and place them in a folder (folder name listed in _init/config file) inside the modules/ folder. It should then appear in your list of extensions available for installation without the need to download from the official extensions repo. This is only for the "extensions" and not for the charts, themes or languages.
@joe: Which path is the latest that needs to be set in version.php ?