I press the "Download 1.13" button and then it starts downloading. It then closes the launcher and opens the Minecraft app. It only opens it for about 1 second then closes, goes back to the launcher and gives me a crash report: "Game crashed whilst initializing game". I rebooted my computer and reopened the launcher but it still didn't work. Opening 1.12.2 works completely fine though.
Not sure if this pack metadata has much effect or if it is something completely different.
The crash report is also included.