LG soundbar not pairing with subwoofer

Hello
I have a LG SN4 soundbar. Some months ago (after a power outage) it refused pairing with the subwoofer, needing one hour of testing and position changes until it finally paired. Now, another power outage left the subwoofer unpaired again, but I have not been able to pair it.
I have moved both to another building, tried resetting the wireless link, reseat radio module connectors, checked radio supply voltages... to no avail (these are the recommended steps from the service manual).
I do not know if the soundbar does not transmit or the woofer does not receive, I cannot test a 5 GHz link.
TIA.
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Saludos
Miguel Gimenez