I've read your FAQ on Calibration and can't seem to get it just right. Do you have any tips for Calibration in Rock Band 4?

WHEN CALIBRATING FOR AUDIO:

Hold the guitar immediately next to a speaker.
In a larger room (or venue), be sure to calibrate off the speaker closest to where the band will be playing.
The volume should be set to a comfortable listening volume.
If you have trouble in a room with a surround system, turning the volume down sometimes helps.
When you are trying to match your strum (or hit) to the beat, don't react to the audio cue. Instead, try to anticipate it and strum at the exact time.
When you strum, grip the strum bar firmly between your thumb and first finger and strum firmly all the way down then all the way up, alternating up and down strums on the beat.

Video calibration tends to work best in darker rooms, so either turn the lights down or angle the guitar slightly downwards away from the light.
You may need to shut off surrounding light sources all together.
Some venues have excessive stage lighting which makes it harder to calibrate.
If the calibration bar is not progressing, cup your hand over the top of the sensor near the sync button. Leaning over the video source with your hand cupped over the sensor will often block out any ambient light that is interfering with sync.

Additionally, if your TV has a game setting, you should activate it.