If you are having difficulty with connecting to a VE.Bus device with a laptop and an MK3-USB adaptor, try the following troubleshooting steps to help isolate the issue.
Make sure the device is connected to a power supply and switched on
Test the cable with a cable-tester and/or try another one. There can be a difference in pin arrangement in some network cables. The required cable is a straight-through cable, not a cross-over cable.
In case you have a GX device available; you can use it to test the MK3-USB.
Make sure the GX device is running v2.23 or later;
The Multi should be disconnected from the GX device's VE.Bus port.
Connect the MK3 USB plug into the GX's USB socket.
Connect the Multi to the MK3 with network cable
The Multi should appear on the GX device.
If all those do not work; the MK3 may be broken, please contact your dealer.
Specific VictronConnect troubleshooting assistance for Bluetooth connections is available here.
There is a known issue that makes VE.Bus firmware updates randomly fail on some macOS laptops. We are working on it; a new VictronConnect version fixing this issue is expected in the near future.
Meanwhile this is the workaround for this: Proceed to update as usual and quickly minimise the VictronConnect window when progress bar is shown because the update starts. After ~20 seconds you can maximise VictronConnect to see the update status. This issue was introduced in VictronConnect v5.9.
For those with a technical background and wondering how, why and what minimising has to do with this: yes this really works, and relates to a power saving mode that has a side effect on serial communication.
You can reset the unit to the factory settings. In the Settings / Product info screen, you can update the devices firmware. This firmware update process will reset settings to the factory default.
If you have additional questions or comments after reading this document, please contact your Victron Dealer who is trained in using this software, and has a known good testing configuration.
You can also ask for help from other Victron users at the Victron Community.