What could be causing low volume?

Cubase
1

For some reason I am unable to raise the volume levels of my VST instruments in my song beyond about -25db (digital scale). Main stereo output is at 0db. No sub groups. Nothing on main bus. Please give me some things to check that could be causing this ceiling. Thanks

2

Maybe you accidentally added volume automation, or something in the Controller Lane of the key editor that kicks it down at the beginning of the timeline.

3

Where are you trying to adjust the level, on the Cubase Channel or a Volume Control internal to the VSTi.

Also there is a Test Tone Generator plug-in you might find useful

Channel Pre-Gain?

4

What instruments would those be? If you load a Groove Agent SE instrument, does it still do it? Some instruments expect CC1 (or other CCs) for dynamics. If the modwheel is completely down, the sound would be weak.