[XenonSurf]

Sorry to say, but read the last Steam threads for the game and you'll discover that you won't have much fun with the Steam version. Problem is it cannot be patched to 1.2.0 (until Steam wakes up some day and uploads the patch) and then because of Steam DRM you still could not upgrade the game with most of the mods in Subsim, until someone comes with a miracle solution.

Ubisoft has nothing more to do with this game, it runs on the UPlay servers.
Check if with your key you can download from UPlay which maybe gives you the 1.2.0 patched version, but I don't know. Instead of asking Ubisoft rather ask Steam support or Uplay.

Now you'll ask: why should you patch and mod, it's because anterior versions and even 1.2.0 are broken and very unsatisfying compared to some serious mods here which turn the game more than ok.
If really you are interested in SH5, get a non-Steam version, doesn't matter which version, important is that you can patch it to 1.2.0.
Or: Get a version of SH3 which should be easier, the gameplay difference is not that big if you mod SH3 whith some good mods like Grey Wolfes or WAC, also you'd have all sorts of sub types to play, which you currently can't in SH5.