OhMyGucciGames

I wanted to play on my server on version 1.17.1 to add some plug-ins. Upon switching the server version, I wasn't able to join the server even when it says it's online. I even tried removing the plug-ins and tried joining in 1.17.1 but to no avail. I was confused and thought it was a bug, but I was able to join the server when I switched it back to 1.18.2. If someone has answers, please let me know because my friend's server works just fine but mine doesn't. Here is a screenshot of the message it says after attempting to join.