Bluetooth can't find headphones on Ubuntu 18.04.4 LTS

Question

Similarly to this question I can't pair my new headphones (Marshall Major III) to my laptop because I can't find the device. I can connect the headphones to my phone (XperiaL1) and my laptop can detect my phone. I read other answers and I tried this solution:

rfkill block bluetooth
sudo service bluetooth stop
sudo rfkill unblock bluetooth

Nothing changed. The strangest thing is that yesterday my headphones were both detected and connected to my laptop!

The output of service bluetooth status

<pre><font color="#8AE234"><b>●</b></font> bluetooth.service - Bluetooth service
   Loaded: loaded (/lib/systemd/system/bluetooth.service; enabled; vendor preset
   Active: <font color="#8AE234"><b>active (running)</b></font> since Fri 2020-06-05 14:25:31 EEST; 18min ago
     Docs: man:bluetoothd(8)
 Main PID: 911 (bluetoothd)
   Status: &quot;Running&quot;
    Tasks: 1 (limit: 4915)
   CGroup: /system.slice/bluetooth.service
           └─911 /usr/lib/bluetooth/bluetoothd

Ιουν 05 14:25:31 piyi-Inspiron-5558 bluetoothd[911]: Bluetooth daemon 5.48
Ιουν 05 14:25:31 piyi-Inspiron-5558 bluetoothd[911]: Starting SDP server
Ιουν 05 14:25:31 piyi-Inspiron-5558 bluetoothd[911]: Bluetooth management interf
Ιουν 05 14:25:31 piyi-Inspiron-5558 systemd[1]: Starting Bluetooth service...
Ιουν 05 14:25:31 piyi-Inspiron-5558 systemd[1]: Started Bluetooth service.
Ιουν 05 14:26:20 piyi-Inspiron-5558 bluetoothd[911]: Endpoint registered: sender
Ιουν 05 14:26:20 piyi-Inspiron-5558 bluetoothd[911]: Endpoint registered: sender
<span style="background-color:#FFFFFF"><font color="#300A24">lines 1-17/17 (END)</font></span>

What can I do?

Answer 1

The Marshall Major III needs to be put in discoverable mode before Bluetooth can detect it.

After you turn it on, keep pressing the (one) button until you hear a second sound, consisting of two tones. After a few moments, the headphone appears in the list.

I suppose this works for many other Bluetooth devices.