Your plugins must be updated.
The update for the G15 plugin already exists.

Client 3.1 has removed the G15 plugin from the client.
You still can use the plugin for your G13,G15,G19, G27 etc. but you have to install it first.

Just open Tools -> Options -> Addons "Browse online" in your client.
Then search for G15 (should show G15 Plugin with author TeamSpeak_Systems_GmbH).
Click on the example picture or G15 Plugin or READ MORE.
Press Install and wait for status "Installed".
Now you can use it. The plugin should be listed and enabled under My Addons

Attachment 14876