Just found this: https://forums.flightsimulator.com/t/how-to-graphics-settings-and-performance-guide-8-18-2020/132407

Quote

G-Sync reportedly may have issues with MSFS, lowering framerates when the window is in focus.

Sounds like GSYNC support is bugged currently, and it's actually better to force it OFF. 😞

UPDATE: it was a problem on my end. Had to do a full 3rd-party driver clean, and it's now working. 

2 hours ago, mikeev said:

UPDATE: it was a problem on my end. Had to do a full 3rd-party driver clean, and it's now working. 

Hey, I'm just curious what your problem was?  I have been troubleshooting g-sync not working for 2 days now with little luck.  I had it working for a very short time, but ever since yesterday it does not look to be working.  My monitor's frame counter is locked at 144Hz and Nvidia Control Panel g-sync compatible indicator is not showing.  This is only the case in Flight Simulator, all other games that I have tested it works correctly.  I have enabled g-sync windowed and fullscreen and did the Nvidia Inspector profile, no luck.  I was hoping whatever worked for you might also work for me. 

Also, I have done a clean install of the latest drivers.

Anybody else have any suggestions? Thanks!

Sure you’ve done this but it is easy to forget: did you add MSFS to the NVCP profiles after downloading the new drivers?

I know I occasionally forget that NVCP doesn’t automatically add all games when a new driver is installed.

8 hours ago, scotchegg said:

Sure you’ve done this but it is easy to forget: did you add MSFS to the NVCP profiles after downloading the new drivers?

I know I occasionally forget that NVCP doesn’t automatically add all games when a new driver is installed.

So, I did a complete reinstall of the drivers using DDU this time.  Checked the profile and made sure G-sync was enabled, fired up flight sim and G-sync was working great.  My monitors frame rate was variable and the monitor also displayed G-sync on indicator as it should.  Shutdown overnight and tested it this morning without touching anything and sure enough not working again.  Checked Nvidia control panel and Nvidia Profile Inspector and all is still set correctly.  I'm not sure what is causing this back and forth behind the scenes.