Question Set prefix in region

Hello, in the plugin Worldguard extra flags, its says that we are able to make chat-prefixes but I have been trying a bunch and it hasn't been working

I used /rg flag <id> chat-prefix Test

It didn't give me the prefix even though I was in the region

I have the plugins installed

• Worldguard
• Worldguard extra flags
• World Edit

Much help appreciated