RE: FSL preprocessing + conn

Dear CONN experts,
I'm trying to import preprocessed rs-fMRI data into CONN for subsequent analyses.
The data have been preprocessed according to FSL's melodic pipeline (which included motion correction with mcflirt, topup-based EPI distortion correction, high-pass filtering and no slice-timing correction since these are multiband, HCP-style fMRI data) followed by ICA-based denoising using FSL's ICA-AROMA. 
I managed to import MNI-space structural data, as well as segmented tissue maps, motion parameters derived from mcflirt and outliers estimated by fsl_motion_outliers for the subsequent step.
Unfortunately, when trying to import precprocessed fMRI data as the primary functional dataset, I get the following error:  

ERROR DESCRIPTION:

Error using conn_menu>conn_spm_read_vols (line 1091)
Error reading file C:\Users\Giuseppe\Desktop\test\denoised_func_data_standard.nii. File may have been modified or relocated. Please load file again
Error in conn_menu (line 656)
[temp,volhdr]=conn_spm_read_vols(title(n));
Error in conn (line 2049)
conn_menu('updateimage',CONN_h.menus.m_setup_00{5},cfile{3});
Error in conn_filesearchtool (line 222)
if length(h.callback)>1, feval(h.callback{1},h.callback{2:end},names); else, feval(h.callback{1},names); end

Am I missing something?
Once I manage to import the data, my idea is to go through functional smoothing and denoising before statistical analyses, do you suggest any additional step?

Thanks in advance for your precious help,
Giuseppe