Jucksalbe: You get a serial number with your purchase. Look in your account on the GOG site, on the game's page there should be a serial number under "More", so you shouldn't need to get a serial from anywhere else.

rychomaciol: It asks for a serial number when trying to play single player like campaigns on Windows 10.

The solutions proposed in other threads like running game as administrator do not work for me.

If I run exec directly form installation folder the game do not when I press cancel after prompted to enter serial. If I run it from GOG Galaxy it will crash if the serial is not entered complaining about Access Denied.

Also cannot find any valid serial numbers as workaround.

It is Settlers 3 Ultimate Edition. The version it says it is is 1.60. I tried re-intalling it already and also didn't help.

Panic! Help!

dayedajajda: I've tried everything - from restarting the game multiple times, trying to clik "OK" on the CD-key prompt, reinstalling the game through the app or the offline installer with auto-update settings turned both on and off, using the "scan and repair" feature in the app multiple times, running the game and installation as admin, running regs.cmd as an admin and looking for a key on my GOG account (yes, in the browser, not in the app), which says the key is used.

Overall, I've spent about 2-3 hours trying the combination of all of the above to get it working and nothing works. I've even contacted GOG support on Saturday and so far I haven't even gotten an answer to my ticket. Today's the fifth day after I've bought the game and I still can't get it to run past that CD-key prompt.

What's worse is... I'll attach a file of the start screen - is it how it's supposed to look like? I don't see any buttons for extra missions or the Amazon campaign, which is strange to me, because I've once owned a Gold Edition bought from a local retailer (I've lost the key and so I've decided to buy it again from GOG) and I think that these buttons were there.

I'm thinking that perhaps something is wrong with my installation in general, so... could someone confirm that this is how the start screen is supposed to look?