power spectral density shows no activity

Question

I am trying to calculate the Power Spectral Density between two conditions recorded over multiple trials with 4 EEG electrodes. To do this I am computing trial-wise averages of spectra by:

1. Apply hanning window to a trial
2. Compute fft
3. Take absolute value squared for power
4. Average over all trials

I have one particular data set that I am analyzing that shows no activity (both baseline and task data are exactly the same/overlapped in figure) and was hoping someone might be able to point me in a direction to figure out why the data appears as it does in this figure: PSD. The raw data looks like a quality EEG recording.