I’ll mention this in case anyone else experiences this issue.
Open Cubase 8.5 project. Back up project. Close project.
Open Back up of the Project. Press play and all tracks in READ automation mode are silent incl Master Bus.
Turn off READ on Group or Master and it is still silent until I moved the fader - now audio plays back. Turn READ back on and NO Audio.
Fix (although I have no idea if this was truly the fix):
I deleted the “defective” back up.
Open Original Project and let it play for a minute.
Back up project.
Open back up and all is fine.