I have this exact same problem, and in my instance I also tried to measure the 12MHz clock that was supposed to come from the X1 crystal. I found no clock
, so it basically means that my board is unable to communicate (through USB) since the FTDI chip has no clock (and thus isn't running). I have a second starter kit board so I wont bother with repairs for now. One should still be able to program the board with JTAG, so if you have one of those you can try to use that and see if it works.
The R23 is basically a shortcut between the 12MHz clock and C8. It seems that older versions of the board had a 0 ohm resistor on R23, so that the MachXO3 could use the 12MHz clock as an external clock source. Since the software connects non-specified outputs to random pins, it could happen that the C8 was connected to a non-specified output and thus rendered the 12MHz clock dead. I think that is the reason they removed the R23 resistor from the later boards.