Hi, i recently added the Cannons plugin to my Minecraft server. We have movecraft, and I set the isSignRequired to true. What command do I need to use or put on a sign to use it? Whenever I put a sign on it, it still says "The classic cannon needs a sign to operate" I'm using an oak sign as it says too.

I put down a blank sign, i did random stuff like [Classic], [Cannon], and others. It won't work, and I must be doing something wrong.

The sign should be attached to side of the barrel, there is no need to write something on the sign. Once you place it a text should appear.
If you make a custom design the sign port shares the place with a chest.
https://media.forgecdn.net/attachments/138/391/2013-03-31_15.28.54.png

They surprisingly started working after I downgraded...

It's still persisting. Downgrading didn't fix it at all... I thought it did.
config.yml: https://pastebin.com/3SZ1Za43
classic.yml: https://pastebin.com/ZXBLrM6A
Screenshot: https://i.imgur.com/0PLvspA.png

Somehow disabling the "issignrequired" lets me place them, but enabling it doesn't.

The sign is only a feature to store information and I would not recommend it since the default database is a better solution.
Can you enable the debugging option in the config.yml and check if there are messages when you click on a cannon with a blank sign?
Which version of cannons and bukkit/spigot are you using?

On your plugin page it says I need to use signs for Cannons if I need to load them on Movecraft. Did I enable the wrong option?
I'm using bukkit/spigot's 1.14.4 version, and i don't know if it helps but I'm using Viaversion to let players from 1.16 play.
Cannons version: v2.5.6

I tested it with 1.15.2 and it seems to work on my server.
I was told there is an new supported movecraft version with supports the Cannons API without signs.
https://github.com/eirikh1996/Movecraft/releases