Welcome to Smogon! Take a moment to read the Introduction to Smogon for a run-down on everything Smogon, and make sure you take some time to read the global rules.
Hmm I seem to be having a similar problem, and I'm on a computer that had it working a few days ago, not sure why it stopped working. I was running Java 18 and updated to Java 20 because it wouldn't work, but alas, no luck.