Raymarine LIGHTHOUSE 4 Operation Instructions Manual page 408

2. Ensure you have installed your Entertainment system(s) in accordance
with the documentation that was supplied with the system.
The Audio app will open in 1 of 3 states:
Audio app displayed
If your Entertainment system is powered up and operational then the player
controls are displayed and can be used to control your system.
Entertainment system powered off
If all Entertainment systems are powered off then a Power icon is displayed
for each connected system. An icon is also displayed to power on All
systems. Selecting the [Power icon] will switch your Entertainment system on.
Selecting the All icon will power on all connected systems.
408
No audio devices found
If the Audio app is opened soon after powering on your MFD, the 'No audio
device found' message may be displayed whilst the network is being
established. If the message is displayed for more than 10 seconds, your
MFD cannot connect to your Entertainment system(s). Ensure network and
power connections to your Entertainment system(s) and MFD are correct and
free from damage and then power cycle your system. If the Entertainment
system(s) are still not displayed then refer to your equipment's installation
documentation for further troubleshooting information.