I bought a flood damaged SLK 320, 2001 off of Ebay. Salvage title for about 10k less than a mint one would have gone for. Every single electrical component in the car was wasted. Took me a week just to get the thing started. Every circuit board had to come out, every electric motor had to be rebuilt, including the hydraulic motor. Pretty simple stuff for us at Tech Edge but time consuming. The problem has mainly been buying new tools for the Mercedes, not having an owners manual (it got water damaged as well), and not having a shop manual. We got the electircal schematics and that helps but it's nice to learn about the normal operations of the car here.
Anyway the windows work fine up and down via the switches. They also work with one touch lowering. The red button still just flashes when I try to lower the top though. I'm sure the car is wanting some condition to be met but I'm just not sure what it is. Do the doors have to be closed? Parking brake on? anything else?