I can’t control the volume on my 520, power and mute buttons are ok but it can’t work with +/- 
It works with my phone and pad only:sleepy: Pls help 
We apologize for any inconvenience caused during use.
Since last week, we have confirmed that the mute button and volume control buttons on the RS520 do not work.
The cause has been found and resolved, and will be reflected in the next SW update.
It may be inconvenient, but I would like you to use it as described below.
Please unplug the power cord connected to the product and then plug it back in.
Thank you
Noted and thanks for your reply.