Interestingly though, if I restart my PC, and activate the short cut immediately, before all else, the launcher loads as normal. If I do anything else, or close the launcher, I then have to restart again.
What Antivirus are you using ? Bitdefender ?
Reason it is likely working before all else loads is something loading is blocking the game, usually the Antivirus
clean boot will allow you to enable one thing at a time to find out which program