What does the error message mean?

I wanted to join minecraft on Alpha.hypixel.net today but then I got this error message.

I was still there yesterday at 11 p.m. It is the Alpha Server from hypixel. I have already restarted Minecraft, but it is still there, does anyone know what I can do?

I haven't played MC for a long time, but I had problems like that, which at first seemed inexplicable, there's always a reason in Minecraft, so:

1. Reinstall the game, uninstall it and then get it back on the Minecraft.net homepage (be careful not to forget your password or account, otherwise your version is gone!)

2. It can also be on the server, see forum if players have similar problems and write to them

3. Unauthorized modifications that do not lead directly to the ban but to the exclusion until you have removed them, just try the Badlion Client for safety reasons

4. Game files changed / deleted, reinstall the game as mentioned in 1

5. Copy the error message and enter it into Google (in 99% there are forums with answers)

That was all

Am tired… Support me if it gave you an idea or fixed the problem