Shimeji | Shimeji are cute mushrooms

I'm currently programming a Python script that opens a file in an different directory that the user enters in an input box. Everything runs fine but the jar file I used for testing doesn't run or show up. I'm using the Shimeji-ee.jar in testing, and at one point its tray icon showed up but disappeared immediately.

I tried running it in command prompt(since calling the jar file using the script is similar to running a file in CMD) and discovered that it only runs as long as the CMD window is open. A few searches later, I've found a way to run files in CMD that keeps it running even after closing the CMD. I wrote it in my script, no errors, but the Shimeji nor its tray icon doesn't ever appear anymore.

I've added a line at the end of my script that is also told to be an efficient way of keeping the script running, but it doesn't work either(could be another mistake here):