Since the server is up and running it's 99% of the time a firewall blocking your game from accessing the internet or opening up the ports needed. It could be that your antivirus has a built in firewall, it could be that windows firewall is blocking it, it could even be that your router blocks it. If not an actual firewall it's all down to your internet connection. The failed to connect to main/front server only really shows when there's no internet connection, or when your game cannot access the internet due to it being blocked by a firewall somewhere as explained above.
Antivirus blocking it?
As mentioned earlier, many antivirus software comes with a built in firewall, and in some cases it's either over protective or not smart enough to let certain applications through. You'd either need to add FeralHeart to exceptions, disable it's firewall temporary and try if it works, or even in some cases uninstall the antivirus all together. Just take note that this is not for everyone if they need someone to babysit their activity on a computer, but also licenses for eventual subscriptions might disappear if you paid for it.
Windows Firewall blocking it?
Not very common this is the cause, but it has happened too. It's fairly straight forward though, it's just to allow feralheart.exe through it/add it to exceptions and windows will let it do whatever. There's nice tutorial videos on youtube on how to do this.
Router Blocking It?(Bit rare but happens)
I do not honestly know under which ports FeralHeart operates which also means I do not know which ones that might need to be forwarded in some cases, but certain routers could cause issues.
There can be many things, and most of the things you'd sadly need to look up and try yourself as the things mentioned here since no one else can sadly do it for you.
But if you think this way:
If it works on another computer but on the same network? It's most likely antivirus or windows firewall blocking the game.
If it doesn't work on another computer on the same network, or the same computer works outside your regular connection, it's most likely your router, it's firewall or other security settings.
