What revision is the speech board you acquired? If it's from the Sys9 era, it may be factory jumpered for different ROM chips which were larger than Firepower's... you'll have to jumper the Sys9 speech board to support the earlier roms, or burn larger roms with the FP sounds. Of course if it's a SYs6 speech board you should be OK.

Every WMS Sys6 + speech game I 've acquired has had bad OEM speech roms; not sure why those tend to go rotten. If you have the means (a rom burner) I would definitely verify they are good before chasing your tail. If you don't have a rom burner, try swapping them into a known good speech board (in another game) if you have access to that.

I've yet to have a ribbon cable go bad, but you can tone them out end to end. A little tricky but worth the effort to solve that variable.

Bad speech roms will cause the sound test to skip the attempt with no blank/pause as well. The boards could be perfectly fine and functional otherwise.

Test your roms first and check back: You can download the rom images from ipdb. Read the physical ones with your GQ4X4, and compare to the ipdb image, one at a time. They need to be perfect before you proceed any further.