I know I did something stupid, and I understand if no one believes.
I followed a guide on Steam, teaching how to unlock the "One Year" and "One Month" achievements using the cheat engine, and now my Universe Sandbox doesn't start online anymore. I've never used this program before, I have no experience with it and I don't plan to use it anymore... And I know I should have never used a program with the name cheat...
I know it's something related to these achievements because this issue began exactly after the achievements were unlocked. And if I start offline, it works perfectly.
Since I felt so bad about this situation, I immediately got in touch with Steam support asking for help, and, if possible, to delete these achievements. Unffortunately they can't do this. So, is there any chance to play this game online again? I love so much the simulations, I even agree to buy it again if necessary.
Again, sorry for my terrible mistake (and for my bad english). And a I appreciate any help.