[emhtuning]

Check your antivirus or security programs. I had the exact same problem with ISTA+ out of the blue. My antivirus (Bitdefender total security 2018) suddenly decided that istagui.cfg was a virus, and silently put it into quarantine. I had to create an exemption for the entire C:\Rheingold folder to correct the issue. You might check for similar issues in the activity log for your security programs.
Missing prerequisites like Java or .NET can also cause a failure to launch.

thanks for the hint , .NET is the issue and i can't sort it out so probably a new Windows installation will fix it as I'm using Windows 10 upgraded from windows 7 so many things are not working properly these days.

I've yet to see a properly working 10 upgrade. There is always some issue with the upgrade. Just do a clean win10 install and be done with it.

I'm doing that tonight , it was upgraded since the time when windows 10 upgrade for offered for free few years ago .