I have installed a plug-in, and it has a bug with it, and when I go to the owner of the plugin’s ‘devforum profile’ it does not let me message him, so I decided to post this issue publicly on the devforum and ‘@’ the creator. What would be the best category for “Plug-in Errors”?
I know this question might be silly.
That is studio bugs. I am asking for plugin bugs.
You contact the plugin developer privately. Try something like Twitter or Discord.
The DevForum isn’t for resolving bugs in third-party apps.
There’s nothing for plugin bugs. So there’s nothing to be done about it on the devforum.
It won’t let me. There is no message button on that person for some reason.
Try following him and refresh to see if it lets you message him.
As I said, try Discord or Twitter— not DevForum.
What is the plugin perchance?
It still does not appear. 
Like Elliott said contact the owner on Discord or Twitter.