The Plugin Author needs to update his Plugin to API Version 26
If you want to downgrade your Client to the Old Version back then,
Please use the following link to download the previous TeamSpeak 3 client version :
http://files.teamspeak-services.com/releases/client/3.5.6/
Edit: I see you have the Control Plugin. Here is an updated Version:
https://drive.google.com/file/d/1X4BX0lFxPg_pyBMX_S65AwCm-Vfqx1kr/view
