MyBB, short for MyBulletinBoard, is a free forum software similar to phpBB and vBulletin.

Issues Solved

This plugin is incompatible with MyBB x.x.xx

This issue occurs when an old plugin is installed onto a new version of MyBB. It does not necessarily mean the plugin is not compatible with MyBB, but fixing the issue will not guarantee the plugin will work.

Solution

Open the plugin (php file) in a code editor
Find the following line: "compatibility" => "xx*",
Change the number xx to your MyBB major version

The number listed contains no dots and does not contain the minor versions, i.e. 1.6.14, rather the first 2 numbers are used. So if your MyBB version is 1.6.14, you would change the compatibility number to 16:

"compatibility" => "16*",