Well since it worked for about two years: Have you made any changes?
Check the plugin configuration and maybe add some delay if you are not using a delay yet.
The TeamSpeak client will always mute the microphone, the plugin just unmutes the microphone again. If the plugin is faster than the client, the microphone will still end up being muted. That's why I added the delay option back then.
The Plugin works on all connected server tabs and will perform the actions on each of them, so being connected multiple times shouldn't matter.