From MemberPlugin

Is the plugin installed?

Check that the plugin shows up in Tools->Add-ons:

Sometimes it will show up there as needing to restart. If it still does that after restarting, then reboot.

Is your group opted-in?

If it's installed and nothing's happening, check whether you see this message:

The plugins will only work if the owners of your group have chosen to opt in. It's possible your group moderators don't know about the plugin, so you could mail them to check.

Getting Debug

Occasionally, you may be asked to get debug information.