Hi @VICTORIALIU,
The AAL atlas is a volume atlas, not a surface atlas.
Check this post:
It is possible to import the AAL atlas, but for sources resulting from volume source estimation:
https://neuroimage.usc.edu/brainstorm/Tutorials/TutVolSource#Volume_atlases
However the process Sources > Downsample to atlas is not supported for volume grids.
In addition, this process is not recommended.
To obtain one time series per scout use the process Extract > Scouts time series
Best,
Raymundo