@ssetgh2 >>> Have you set Shadowplay to record the desktop? If that is NOT on, Shadowplay won't record any Trainz window.
1.) Open Geforce Experience
2.) Clik the settings icon (Gear), top right
3.) Left Panel, General Settings, then center column, tik the gameplay overlay switch.
I have just been using GeoForce Experience earlier today
Press ALT + Z key click on the Record Button then click on Start Recording
to stop recording
Press ALT + Z key click on the Record Button then click on Stop Recording