I thought I posted this earlier but maybe not. I was having the same problem with NXStudio and tried the same things you have tried. Having a tech background I realized when you uninstall some pieces of software they often do not remove everything. So somehow, a setting is being retained even though you uninstalled it. My solution was to uninstall the software, then go through the files and remove every instance of anything with Nikon in the name. If you are on a windows computer, you can use File Explorer to open your hard drive (usually drive C), then use the search feature of File Explorer to look for Nikon. After deleting all the files and folders associated with Nikon, be sure and empty you Trash/Recycle Bin. Then reboot your computer and reinstall the software.
If it still doesn't work, you may have to open the Registry and do essentially the same thing. The registry is what controls your computer and Windows, so if you aren't familiar with it you may want to ask someone to help you. One wrong move and you could "brick" your computer.
I told Nikon support about my solution and at first they just said they couldn't recommend using the Registry and they were not sure about the uninstall process. They told me they would check with their software engineers to verify the uninstall problem I described but I never heard anything after that.