Hi-
So, you have bandpassed your data, so presumably your time series are just LFFs now. That means that fALFF cannot be estimated, since there is not the "full" spectrum to be calculated for the denominator of the ratio.
For ALFF, you mentioned in an email that your data were also censored when going through your pipeline. At present there isn't a function for estimating ALFF when the data have been censored (because there are missing time points). I had started a function that could potentially do this, but will have to revisit it.
-pt