Was an answer ever found for this?
I am relatively new to DCS, and I'm trying to go through the training, but nothing happens when I press the space bar so the training will not move on.
Worryingly, from Googling for a solution it appears I will run into the same issue when I start to try to do missions, as I see there is a lot of press space bar to advance required in missions too.
AFAIK I have not mapped space to anything else in DCS. Whilst I can fire guns, pressing the gun trigger does not advance the training either.