DarkFib3r

Thanks for tips and the link, I was able to get it to run exactly as you said:
Activate and enter old CMSF1 activation code Close Activate and enter old CMSF1 bundle activation code Close Activate and enter new CMSF2 bundle activation code Play And it works!

Having CMSF on your PC or not has nothing to do with it, this is not a typical upgrade, it is a new game.  You need to go to the my accounts page, go to your CMSF1 purchase and grab the activation code there and apply that to your activation.  CMSF2 knows nothing about your CMSF1 without using that activation so you can't activate the "upgrade without first proving to it that you owned CMSF1.  Basically what you want to do is run the installer, launch the activation shortcut, paste in your CMSF1 key, repeat with CMSF2 key.  In effect you need 2 keys.  One to show you own CMSF1 and the second to show you have CMSF2.  This only applies to folks purchasing at the discounted upgrade price for those who have CMSF1.
See this thread for some of the responses from Steve on this.
 

I am having the same problem - I bought the CMSF1 Big Bundle Upgrade. I activate it fine, but it shows me the activation splash screen with no visible text, but if I copy and paste it to a text editor, it says:
Game Title
Your trial has expired. We hope you enjoyed it!
You can unlock the full version by clicking 'Activate'
Instant Activation
When you enter your serial this app will be fully activated instantly. No Redownloading needed!
Unlimited Shelf-Life
After activation this application will be yours forever.
Technical Support
Having issues? Contact us to get support with any technical problems you may be experiencing
Exit 
Activate 
Buy Now
People say you have to tell it about CMSF. Where and when do you do that? I have CMSF installed successfully on my PC already. And CMSF2 is a new install. Any tips are appreciated!

I use breaching charges and BLAST command.

First I arrange an adequate fire support group of 2-3 MG teams hosing down the building I'm about to take. Then I send an infantry group beside the building wall by QUICK, followed by BLAST to enter the first floor. Sweeping up the second and the third floor works brilliantly with BLAST as well.