Thanks for the idea, but as I've already mentioned, there's no trace of it in the Task Manager -- not under Apps, nor under Background Processes.
Also, I might point out as an aside, that I have actually had multiple instances of Trainz running in the past (by accident), albeit very slowly.
Yeah I've done it by starting Trainz from the Launcher as well. That was quite confusing because each version was fighting for resources and was throwing up fits while saving.
No trace... Have you changed or updated your antivirus program? They can and will kill applications it doesn't like. It'll also wreak havoc with your data. I recommend excluding TRS2019, and it's folders, including your data too, from scanning.
In the event that it still won't start, and you have to reinstall, you won't lose your data.
1) Copy your user data folder to a "safe place". This is always a good thing to do especially if something weird has happened.
The folder is located here by default:
C:\Users\<Your LOGIN Name>\AppData\Local\N3V Games\trs19
In a folder named build something. (Like this here: build 9k0qtg991)
The something is a bunch of letters and numbers.
If you have multiple ones, copy the folder with the most recent data. (open the folder and check the dates of the content).
2) Uninstall the application by deleting the folders directly from your hard disk. The uninstaller is broken once you've updated the program.
3) Reinstall the program.
Go through the motions of letting it choose it's own data folder, etc.
Once done:
1) At the Launcher, open settings.
2) Click on the Install tab.
3) Click on the ... on the right.
4) Browse to C:\Users\<Your LOGIN Name>\AppData\Local\N3V Games\trs19
5) Look for the build something folder with the same letters and numbers as the one you copied.
6) Click on that.
7) Click on the select folder.
This will remember all your settings you have already including your username, password, and other setups.
You'll be asked to restart the program. Do as instructed, and you should be up and running.