I think the file is corrupted.
At the start with the gong hits, after a smidge of editing and adding drums, there is a huge wall of noise from the headphones, so I deleted that part assuming I'd just need to rerecord them. No go, there is no sound whatsoever from that track, or other tracks for that matter for the gong. I know it is not my setup, as I opened a new project and with the same settings, the sound came through no bother.
Looks like I'll have to try and recreate what I've already done, not easy as I wrote nothing down, I know I should, but well...
Any help in recovering it would be greatly appreciated.