Ok, I think I know what your issue is, and more importantly the solution.
I believe that when you updated to 1909 you got a "DCH" version of a video driver installed by default. From what I can tell, DCH is new to Windows 10, and may have some benefits down the line, but for now it's not ideal for 3D and we still want a "standard" driver. The thing is, once you have a DCH driver installed, you can only install further DCH drivers on top of it. When attempting to install a standard driver on top of a DCH driver it will see a mismatch and prevent you from doing so.
So, now, for the solution. Thankfully, it's a simple matter of DDU, however you have to enable a specific setting in the options menu. Can't remember the exact wording, but essentially it is to "not download a new default driver on Windows startup". If you don't have that option set then even if you DDU, once you restart Windows the first thing it will do is download and install a generic DCH driver. If you have that option set, then after you DDU and restart then Windows will simply use a standard generic driver that Windows already has, and then it will allow you to install newer Nvidia standard drivers.
Actually, there are 2 possible solutions. The 2nd, of which, is that
there is a DCH version of the 425.31 driver, so you could simply download that and install that and you should be ok.