I just finished my first play through and did Denver, then Steeltown, and after Aspen did Cheyenne Mt.

Turns out it's because internet connection, lol. This is madness. Is there any mode to fix this? Soon I'm going to place without internet and I want to finish this with all content...

There shouldn't. At least not a workaround within Steam ToS. It's explicitly stated as a minimum requirement on the DLC store page.

Additional Notes: Internet connection required for DLC ownership validation.

Not a great design for a single player/LAN game imo but very common nowadays sadly.

Originally posted by Heau:

There shouldn't. At least not a workaround within Steam ToS. It's explicitly stated as a minimum requirement on the DLC store page.

Additional Notes: Internet connection required for DLC ownership validation.

Not a great design for a single player/LAN game imo but very common nowadays sadly.

Common? I own around 300 games on my account and it's first time I see this.

It's definitely not the first time I see a similar discussion.

There are a number of modern anti-fraud tools (i.e. ensuring that a software copy is legit rather than cracked) that are adding internet connection requirements to games. The last time I saw a similar discussion, we had people suggesting that the money they lost from reduced sales was probably more than what they would've lost to fraud if they didn't use those tools. But at the end of the day, it's the developer's/publisher's judgement call.

I'm not convinced that the average prospective buyer looks at minimum requirements and rule out content that require internet connections on these grounds meaning it's probably still net profitable but I'm still not convinced its the right solution for the root problem.

Your best bet might be to reach out to the dev/publisher describing your situation hoping they have some custom workaround.