I had this error earlier today. My RFXtrx has been working flawlessly for about a year. The issue occurred when I moved my VeraSecure. I restarted the Vera then, realising I hadn’t plugged the RFXtrx into the USB, I plugged it in. In short, I think the issue was that I restarted the Vera without the RFXtrx plugged in.
I received the error “RFXtrx lua startup failure” and lost contact with all my LightwaveRF switches.
After lots of bumbling around, I found the issue. It had forgotten the serial port settings. When I looked at it, most of the fields were blank.
Plug the RFXtrx into the USB port.
On the menu: Apps > Develop Apps > Serial Port Configuration
There you should see the following or similar:
Name: ftdi_sio (I assume this is provided by the system)
Device number: usb-xhci-hcd-1 (I assume this is provided by the system)
Port: 3841 (I assume this is provided by the system)
Data bits: 8
Stop bits: 1
Used by device: RFXtrx controller (Select from drop down)
Reboot your Vera: Settings > Net & WiFi > Reboot.
Also check out this post on Vesternet which has a seciton on setting up the serial port.
Hope this helps someone.