How do you sync the clock on it?
Discussion
So it wasn't set. Thought sure that would be it. I set time via FM RDS and confirmed it set the system time from that. Went back to FT8, still no decodes over 4 full cycles.
I would try to feed audio from the radio into your PC to help troubleshoot this. Maybe its internally in lower sideband mode or the audio is distorted or filtered.