I have followed all the steps explained in the group analysis tutorials, and the mri_preproc seems to have ran correctly but once the mri_glmfit is launched i get the following error :

Computing normalized matrix
Normalized matrix condition is 38.1502
Matrix condition is 1.78431e+12
Found 149926 points in label.
Pruning voxels by thr: 1.175494e-38
Found 0 voxels in mask
ERROR: no voxels found in the mask
  make sure at least one voxel has a non-zero value for each input