Hi Damian,
Long shot, reinstall firmware, but this is a very long shot.
Looking at the schematic, I think you could first try to veryfiy if there is any RF signal comming out. Junction between C510 & C511 and output of T501 by using a multimeter and RF Probe.
If RF signal is comming out there, then in the next step I would check if it passes LPF filters junction of L514 and C526.
Just for reference I take it that SWR limiter is OFF, dummy load connected.?
Out of interest, did you build 9 or 12V version.
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73 de Marek SP9TKW
Marek SP9TKW