The possibility of failure:
1. The data cable between the laser and the marking contorl board is in poor contact (re-plug or replace the data cable).
2. The optocoupler of the laser marking control board is burned out.
3. The laser is broken (mainly the signal part).
There is a high probability that it is a problem with the data cable. Just re-plug or replace the data cable.
Related: current LMC board is not for Fiber Laser, Error: IPG Laser: Power error!