Apparently, I have some sort of issue with a plugin, specifically the Decal Expansion one by Marco Handres. It still seems to be working on my offline worlds, but the plugin's features dosen't seem to appear online. I tried to see if the plugin was in the plugin store but it didn't appear there, either. I even traced down the file path, but it doesn't seem to appear at all.
I would really appreciate it if you'd find the cause of the error. thanks.