Hi all, I have been also hit by the extreme slow NX Studio on my 2 PCs. Nikon support did not find anything except they suggested to create a new account just to try and use NX Studio, and it worked perfectly well. So this means there was something in my main account that was incompatible with NX Studio : another software or some parameters. Nikon support concluded I had to contact the hardware manufacturers, which is the most stupid answer I have had on that topic. FYI, all my other software such as Lightroom or Capture NX-D were working perfectly.
But since I just installed a new PC, I tried to find out what the issue was. I installed NX Studio as the first program and it was very fast. Then I made all the other installations and parameters setups step by step, to check after each step if NX Studio was still running well. And I found out! The faulty program is my cloud access and synchronization tool, pCloud (a Swiss cloud company, which provides a nice solution btw, that works perfectly well. Each time I quit this pCloud program, NX Studio immediately launches if it was blocked, or allows me to look at my albums and open a photo at a good speed. Even on my 15 yrs old PC.
I have no idea why it is so. I will try to inform Nikon support, and also pCloud and see what they say. Meanwhile I am just stopping my cloud sync when I want to use NX Studio. Not optimal since my reworked photos are not automatically backed up, until I close NX Studio and relaunch the cloud software. But better than nothing.
I hope this may help people who have more a less the same issue. The best way to test is to create a secondary account, install NX Studio first, check it works well, and then install all the other softwares you have, one by one, until you find out which one is preventing NX studio to launch...