Hi
Read the article (in the link) and learn what to do. However since it was professionally installed there are a couple of options:
If you purchased everything through the installer then IMO they are responsible to get things working properly including replacing the Amp if necessary.
If you purchased your hardware yourself then the installer should trouble shoot every thing. If they cannot resolve the issue you can contact Sonos Support as the link suggests or you can return the amp to place of purchase and request a replacement. Replacement depends upon if you are still within the proper timeframe.
https://support.sonos.com/en-us/article/sonos-led-lights