An addition to my previous post.....

Yesterday, after advancing the throttles to 100%, and upon reaching 80 knots, I pressed the EPR button, but it failed to engage! It only engaged after takeoff, and at 400ft AGL, I pressed the AP button, then LNAV, and VNAV (it was turning on the VNAV that engaged the EPR). This was in the newly installed 757 III freighter for FSX-SE. I'm just telling which version it happened in, because I generally find that the performance of the 757-III is the same across all platforms (FSX/SE/P3D3/P3d4), of which all are istalled on my computer, but with FSX, I can't activate SP2, or Acceleration in Windows 10 at the moment.

I must admit that I switched to turning the VNAV, and LNAV on after switching the AP on, due to an earlier problem, where having them on, and after takeoff turning on the AP, the 757 turned them off, and used VS Hold, HDG Hold instead. I haven't gone back to the old way, but I really should have (I got into a different habit :O). That could be the reason why the EPR isn't engaging!