Seamoth sonar doesn't work

[Black Hole Sun]

Sonar doesn't work in any of my Seamoths. This happens in Windows and macOS, and Freedom and Creative modes. I can use it fine in my Cyclops, so it's not that I don't know how to activate it.

[Freedom Manager]

You have to install the Sonar Module. Also you must select the hotkey number for it ( 1, 2, 3, 4 ) and then right click. I don't know if you already knew this, but just in case.

[Black Hole Sun]

It wasn't right-click (that's the lights), but I tried the left click and got it! I was used to the cyclops just running continuously, I didn't think to try a mouse click. Thanks!

[dreamrider]

There are TWO types of sonar for the Cyclops.

The near-field local sensor is the holo display just to your right and down a little when you stand at the Cyclops wheel. It mostly detects / displays the current noise profile of the sub (the inner pale blue sphere), and threat creature indicators within ~ 100m of the sub.
This display comes as a standard part of the basic Cyclops.
I'm actually not sure if the game ever refers to this system / display as "sonar".

There is NO PARALLEL to this system for the Seamoth.
But then, the visability and maneuverability is much better.

The system that the game refers to usually as the Cyclops Sonar (module) is a long range active sonar pinging system, similar to the one you can build for the Seamoth.
This is an additional technology that you can find in the game, and add to the Cyclops by building and plugging in a module at the upgrade station.

FWIW, it is extremely unwise to turn on and run the long range Cyclops Sonar continuously. (Though I am pretty sure that is not the system you meant in your post above.)
If run for a prolonged time, it attracts aggressive creatures, and it is a terrible power hog.

[Freedom Manager]

Lol oops