Hi!
According to your error message, it seems response group crashes with the announcement service.
In this case, we recommend you try to restart the RGS Service on the front end server to see if it can be fixed.
Besides, If your server is Skype for Business 2015, you can try to install the July 2018 cumulative update 6.0.9319.534 for Skype for Business Server 2015, Response Group Service. For more details, you can refer to:
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