2019-10-12 14:12:54 [v:2019.10.1] [main] [CRITICAL] Failed to install Paradox Launcher:
exit status 1603
Running steam.exe as the Windows Admin user should get past that error. Are you sure you did that successfully?
Then here's a more elaborat eprocess that a user came up with, which helped them:
1. Uninstall the game. Delete the Paradox folder in My Documents.
2. Delete all files and folders that reference the Paradox launcher in AppData and in SteamApps
3. Restart
4. Start Steam by right-clicking and choosing Run as Administrator, or whatever your version is and then install the game
5. Verify integrity of game files
6. In steamapps\common\Europa Universalis IV doubleclick on the launcher-installer-windows program and choose "Remove"
7. in the Steam Library, right-click on the game and Open it
8. The Launcher installation will come up, and when it allows you to choose the pathing, set it to an empty folder, like "C:\Users\<UserName>\AppData\Local\Programs\Paradox Interactive\new\" the \new\ being an empty folder created for this purpose
9. The new Launcher will come up, and in the upper left corner alert you that there is an update to the Launcher and you need to close and the rerun the game. Do so.