For some reason PS now stops you from saving 16 bit straight to jpeg.
This post says you need to convert to 8 bit:
Photoshop won't save from PSD to JPEG | Adobe Photoshop Family
But when I tried the only thing that worked for me was to 'Save a copy'.
This post says you need to convert to 8 bit:
Photoshop won't save from PSD to JPEG | Adobe Photoshop Family
But when I tried the only thing that worked for me was to 'Save a copy'.

