Try changing the tickspeed in console when its starting up. If that doesn't fix the issue you can attempt to fix this by going to the Danger Zone and clicking Repair Files. If those 2 solutions don't work you're going to need to contact support and they should respond to you soon through email.
To expand this, this is correct but the reason Zero Tick Farm's don't work is because PaperMC (A fork[edit] of SpigotMC) disables this since it was originally a bug. You would be able to disable this, however spigot.yml is locked
Using the plugin Multiverse and VoidGenerator you can use this command:
/mvcreate <WORLDNAME> normal -g VOIDGENERATOR:PLAINS
Once it's done creating the world, you can visit it using /world or /mvtp
You aren't able to delete a server, however you can reset it in the Danger Zone section and clicking Reset Server. Restarting the server after that will show a completely wiped server. You can also rename the server in the dashboard.
Essentials allows you to do this in their config with the "allow unsafe enchantments" option, set that to true and run "/ess reload" and you should be set. You can also use Item Editor to also set a high enchantment amount
TuSKe has an issue where you reload all scripts is crashes the addon. Never reload all skripts. Reload them one by one using "/sk reload <scriptName>".
Also this should be in Skript Discussions btw
You can unban yourself by using "/unban-IP <your masked ip>" You can find your masked ip in the banned-ips.json file in the root directory of the file manager.
I'm pretty sure the Repair Files button is able to fix this issue, try going to Danger Zone and clicking Repair Files, restart your server and see if it's fixed
If you have the plugin named "CoreProtect" you can do "/co rollback r:100 t:<time example: 1day>" and that should rollback the world, if you don't have the plugin unfortunately there isn't a way to roll your server back that I know of, sorry