Most cloud storage services do not provide direct downloads. The URL you have is just for requesting the actual, secret URL they generate on the fly, and which you get only if you use their special app or web page. In other words, they intentionally make it so that tools like wget and curl will not work, and it is probably a violation of Mega's TOS to even try. You may be interested in the free software jDownloader if you have a need to download from a variety of cloud storage services.
