Does anyone know how to fix it? I haven't used Minecraft in a while, it comes up with "Unable to save download. netty-all-4.1.9.Final.jar"

 

Maybe cause you are using 1.12.1 as the server doesnt support that version yet.
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For more info ^^

 

No, it's not that it's the actual minecraft client

 

Idk it may be the issue with Java. Not too sure

 

I've had the same error before. Reinstall Minecraft ( Remove the folder .minecraft as well ).

 

You could go to your downloads and click on your minecraft download and then click repair?

 

When did you last play Minecraft? I suggest just reinstalling the entire game.

 

Only a few months ago tbh, too much effort to reinstall might try in another few months

 

Come on, it ain't that much hard work.. lol