EDIUS proceeds audio normalize by using waveform cache. It does not work in either following case:

1. Waveform cache does not exist
EDIUS generates waveform cache (.ewc2) next to the clip. If already exists, try to regenerate the cache in clip properties (Audio info > Refresh Wave Data). If regenerating the cache fails, free disk space might not be enough. Move the clip to another location then perform generate waveform cache, and then perform audio normalize.

2. Waveform cache is being generated
Perform audio normalize after finishing generate waveform cache file.

3. Hi-res clip off-line
You cannot perform audio normalize for a clip that is hi-res off-line. If you load XDCAM clip from a media to the Bin or timeline, hi-res may be off-line. Register the clip via [Add and Transfer to Bin] context menu then perform audio normalize.