Just bricked my sim somehow. After running the 40th Anniversary update, I noticed a pretty good loss in frame rates, so, in an effort to help frame rates, I switched the game direct X settings from direct X 12 (beta) back to DX 11. But I recently installed the Nvidia, game ready driver, which I believe is optimized for DirectX 12. After I switched the setting in the sim, it said it had to restart the simulator in order for it to take effect. But now the simulator won’t start up without getting an error, saying I am having a graphics device problem, “this may be due to graphics card, overclocking, overheating, or due to a driver, fault”. I don’t know of any way I can change the simulator settings back without the simulator being open. my GPU It is a Nvidia GeForce, GTX 1080. I have run a clean install of the latest game ready driver, (at least 5 times now) and even tried the Studio Driver. Neither worked. My computer is equipped with two GTX 1080 cards, so I opened her up, cleaned out all the fans, checked all the connections, and swapped the two GPUs to see if the one had failed replacing it with another one would help. Nothing has worked. One user on Facebook suggested deleting the file “UserCfg.opt”, in C:\Users\YOU USERNAME\AppData\Local\Packages\Microsoft.FlightSimulator_8wekyb3d8bbwe\LocalCache, as it is where the sim saves all of the settings. The game should recreate a new file when starting back up. This also did not work. If anyone can help I would appreciate it tremendously! we all waited months for this update, and I only got to try it for about 15 minutes!
open the UserCfg.file and change the settings back 
( DX12=on is then 1 , instead 0 )
Where is this CFG file?
you mentioned the place allready in your post
C:\Users\UserNamer\AppData\Local\Packages\Microsoft.FlightSimulator_8wekyb3d8bbwe\LocalCache
You mentioned you removed that file.. well, now just try to open the existing file with an editor and check which setting is currently set.
It hasn’t generated the new file yet, because the sim won’t launch. It has to launch first to generate the file, I think. Its not in the folder any more, and I’ve also emptied my recycle bin. 
Sorry.. I thought you were referring to a different file.
then you are possbile more affected from
My recommendation: set a low fps limit in nvidia control center for a test-run ( e.g. max 30 fps ). Also, second test is to disable HAGS in case it is enabled. But there are also other hints in that topic.
You can also check the windows event log, whether you find exact error message.
ähmmm… not sure, but that sounds like as the gaming services have an issue. I’am not an expert here, because own Steam version and I have’nt gaming services installed.
But we have some topics how to “reinstall” and also found that FAQ
But how that relates to the dx12->dx11 change, I dont know.
Thanks to anyone who tried to assist. I don’t know how but the issue seems to have worked itself out, and there was a huge update. After the update, you can see a note in the settings about memory issues when switching between DX11 and DX12. Weird. I think I’m up and running again. Thanks to those who were willing to offer some advice!
I thought you had the latest update ( 40th Anniversary ) already installed 
But anyway.. happy flying now
I did. I was flying the new aircraft yesterday… It either ran an update or did a clean install, I don’t have a clue. It took like 5 hours though. A lot of my settings were reset, to be expected after deleting the file I deleted, but now a LOT of my community folder items are no longer showing up in the sim. I have no Idea what is going on at this point. Whatever installed, update, or game itself, I didn’t tell it to install anything. I just tried to launch the sim same way I have always done, same way that has been giving me huge issues over the last 24 hours, and it came up on the screen like an update. First I was just elated that it actually launched without the error message, clicked download to install, and now I’ve been spending all day reinstalling the world updates and my addons from the content manager… Then I started noticing things that were in my community folder were also not working. I don’t even know…