Dear experts

I try to estimate a second level batch with a 2-sample test design and always receive the error message:

Error using spm_est_non_sphericity (line 196)
Please check your data: There are no significant voxels.

Error in spm_spm (line 418)
    [xVi, am]  = spm_est_non_sphericity(SPM);

Error in spm_getSPM (line 234)
        SPM = spm_spm(SPM);

Error in spm_results_ui (line 261)
        [SPM,xSPM] = spm_getSPM;

Error while evaluating uicontrol Callback

I have checked the contrast images for all included subjects and all of them show activation. Do you know what went wrong here?

Thank you very much