When I try to make a Direct/IP game the "create" button is greyed-out / I cannot click to create a game.

I heard I need a CD key to create even offline LAN games. Is this still necessary and if so, where should I insert the Key? It never appeared as an option during the installation or in the game Menus.

Thank you in advance.

If you mean Empire Earth II, then you can install UP1.5 which takes care of CD-KEY problems: https://www.ee2.eu/patch/
Then you're able to play normally using the Multiplayer Lobby.

Thank you, this means there is currently no option to insert/register the key without the unoffical patch?

There is... In... Unofficial Patch 1.5 Configuration Utility. Please take a look: https://i.imgur.com/et22Grl.png

The problem is greater than just inserting the CD-KEY. First of all CD-KEYs of both players need to be different.

Second, even when CD-KEYs are correctly inserted, the game has too many functions that may bug and cause disconnect during the active game. Those functions have been modified in UP1.5.

Third, even if CD-KEYs are correctly inserted, the LAN mode is too buggy and too problematic to use.
Unofficial Patch 1.5 has a Multiplayer Lobby, which also helps to establish local (LAN) connections.
I wrote little more about it on this website: https://www.ee2.eu/multiplayer/help/#lan

Fourth, in Unofficial Patch 1.5 the ping (delay) between players have been significantly reduced by this update: https://www.ee2.eu/patch/changes/#156020 For example players on the local network usually had ping of 40-50 ms, now it's only 3-7 ms. This is because for unknown for me reasons (maybe in 2005 it mattered) there was a fixed thread sleep time in the game process. This change has no negative effects, as after this update in 2017 over 100 000 multiplayer games have started.

Fifth, playing without Unofficial Patch 1.5 in 2020 is not enjoyable. There is a support for all screen resolutions, DirectX 9, Antialiasing, better camera zoom, more options in game (population, resources, ceasefire), option to disable crowns system, cycle time of day, new climate (Tundra), and many, many more features. And all of this is fully configurable by the UP1.5 Settings window which I showed in the screenshot above.

I understand that using "unofficial patches", and other third-party programs is risky, and it's smart to avoid those things. However, you could make a quick research about UP1.5, that those patches were released since 2011, and there are no negative feedback / opinions from users. After all, reading the huge changes log of monthly updates: https://www.ee2.eu/patch/changes/ should be the biggest proof of good intentions in working on this project.

Here is the video showing "How to play online" if you decide to give it a try: https://www.youtube.com/watch?v=uhZ7ESYLLSo

the patch contains malicious files. don't unload it. contains spam and if you turn off the option to send information it becomes unstable

Do you have any proof about files being malicious? Or you just came to leak your frustrations that something doesn't work correctly on your configuration?

Antivirus scans of the newest Launcher files:
https://www.virustotal.com/gui/file/a33e7c2813e2155e7d3468727001d37000bb5818c59ed3145377ae1e003cfdef/detection
https://www.virustotal.com/gui/file/c53cfbae8003a207a9cf4858ee03abe48c2da146c9c8141fd701e761afef6ae6/detection

None of serious AV programs detect it as dangerous, which is rare for new programs.

Of course you didn't bother to learn why some of NEW features, that have never existed in EE2 won't work when the statistics system is disabled. It's all explained here:
https://www.ee2.eu/help/#grayedoptions

By the way, it seems that you've just been using our Multiplayer services today afternoon, using nickname "gatof"? How come you're not afraid to continue using a software that you call "malicious"? Isn't it a one, big hypocrisy?