In a dual Victron MultiPlus parallel installation, one unit dropped off the VE.Bus network. Root causes included: mechanical instability of the MultiPlus power button (intermittent contact), VE.Bus RJ45 cable fault or loose connection between units, and configuration drift after a deep discharge event. The MG Master contactor had disengaged due to loss of VE.Bus communication, leaving only one MultiPlus visible in the Victron system. Deep discharge during winter lay-up triggered the cascade.

1. Physically inspect both MultiPlus units — verify the power button on each unit is fully pressed and latched in the ON position. The button must click firmly; a partially pressed button will cause intermittent VE.Bus dropout. 2. Inspect the VE.Bus RJ45 cable connecting the two MultiPlus units — unplug and re-seat at both ends. Replace cable if damaged or kinked. 3. Reboot the SmartLink or Cerbo GX: hold the button for 3 seconds until the unit restarts. Wait 60 seconds for VE.Bus to re-enumerate. 4. Verify both MultiPlus units appear in VictronConnect after reboot. If only one is visible, the VE.Bus cable or the offline unit's button is the fault. 5. If the MG Master contactor is not engaging (no audible clack), verify VE.Bus is healthy first — the contactor requires a valid VE.Bus signal to close. 6. Allow the system to charge to a minimum of 60% SoC before attempting full load. Deep-discharged batteries may cause repeated dropout during high-current inrush.