Global server where all available Freelancer servers were listed is offline for quite a while now. As Microsoft was planning to drop support for Freelancer in the next months, current problem doesn't look like an occasional failure.
However, there are alternative ways to connect to Discovery Freelancer 24/7 (and any other Freelancer server) easily.
I. Change Freelancer shortcut
First of all, you need a valid Freelancer shortcut. The shortcut should point to Freelancer\EXE\Freelancer.exe file.
Amend Target: field of shortcut properties with ip:port, so that it looks like
After you double-click this shortcut, Freelancer will launch like it always does. However, when you'll select Multiplayer in main menu and choose either LAN or Internet, you'll immediately see Discovery server, if it is online. There's no difference between LAN and Internet options, except when using Internet the game will attempt to connect to global server.
After installation, open this link in any browser:
freelancer://207.192.239.85:2302/
Freelancer will launch, and Discovery will immedately appear in server list, like described in (I). As an alternative to the link, you may use this internet shortcut: