I am having a serious issue where Unity Editor will not launch. If I click the icon on my desktop, all I get is a grey box. If I try to open Unity Editor with a scene file, I either get nothing at all showing up, or I just get stuck on the Unity Editor splash screen. I have tried to reinstall Unity Editor, but that did not work. I am running Unity 5.4.3f1 on Windows 10. Any help is appreciated! Thanks!
Is this the first time you install Unity? If yes, install an older version, 5.4.1 should do, then launch it once, uninstall it and install 5.4.3. When uninstalling 5.4.1, do not delete the folders that are in your AppData directory.
I had 5.4.2, which was working for a day, and then it suddenly stopped working. I had the grey screen issue right after the first time I ran, but after that I was able to launch with a scene file, but even that isn’t working anymore.
Okay, in that case uninstall Unity and delete all the files in your AppData directory; then install 5.4.0f3. Once installed, launch it, then uninstall it, install the current version without deleting the unity folders in your AppData directory.
That worked! Thank you so much! I am now able to see the project selection window, and the projects load.
I’m glad it worked. 
@superpig This means that a certain problem is still there in Unity 5.4.3f1.
Necroposting because I NEED this to work. Tried this method along with a dozen others, still grey screen.