Can not connect Bluetooth audio device to Raspberry Pi

I am trying to connect via Bluetooth, an no-name amplifier with Bluetooth input (bought from Ali) to Rasperry Pi-nano with USB BT dogle. This RPi model does not have a graphics card, therefore all operations must be performed via CLI.
The amplifier connects to a Samsung smartphone without any problems and it is possible to play sound from Samsung through this amplifier. And without entering a PIN.
However, I cannot connect the amplifier to RPi. Below, the status of the device as seen by Bluetooth daemon on Rpi. As you can see, the attempt to "connect" ends with an error. What else do I need to check/add/change to get connected?

Code:[bluetooth]# info 01:28:6F:AD:B5:4D
Device 01:28:6F:AD:B5:4D
Name: XY-P15W
Alias: XY-P15W
Class: 0x340404
Icon: audio-card
Paired: yes
Trusted: yes
Blocked: no
Connected: no
LegacyPairing: no
UUID: Audio Sink (0000110b-0000-1000-8000-00805f9b34fb)
UUID: A/V Remote Control (0000110e-0000-1000-8000-00805f9b34fb)
UUID: PnP Information (00001200-0000-1000-8000-00805f9b34fb)
Modalias: bluetooth:v05D6p000Ad0240
[bluetooth]# connect 01:28:6F:AD:B5:4D
Attempting to connect to 01:28:6F:AD:B5:4D
Failed to connect: org.bluez.Error.Failed
[bluetooth]#If more information is needed, I will provide it immediately.