Hello, I'm also trying to solve the same problem.

I want to compute the correlation between the seed region (ROI) and the rest of the brain. I'll start with how I created my ROI.

First I created a mask of the left precuneus using the TT_Daemon atlas. Then I warped it to MNI space using 3dWarp.

whereami -mask_atlas_Region TT_Daemon:left:precuneus -prefix Lprec
3dWarp -prefix L_precunn -tta2mni Lprec+tlrc

Since I have received an error on input dataset grid mismatch, I re-sampled the mask to the fanaticor dataset before using maskave.

3dresample -master errts.subj.fanaticor+tlrc. -inset Lprecuneus+tlrc -prefix L_precuneusM
3dmaskave -mask L_precuneusM+tlrc -quiet errts.subj.fanaticor+tlrc. > L_precun.1D

Now I wanted to correlate this ROI to the rest of the brain using 3dTcorrMap, but received the following output:

3dTcorrMap -input errts.subj.fanaticor+tlrc. -bpass 0.01 0.1 -Gblur 4 -seed L_precun.1D -mask mask_epi_anat.subj+tlrc. -Mean Lpre_Mean
++ 3dTcorrMap: AFNI version=AFNI_19.2.01 (Jul  3 2019) [64-bit]
++ Number of voxels in mask = 107829
 + bandpass: ntime=198 nFFT=198 dt=3 dFreq=0.0016835 Nyquist=0.166667 passband indexes=6..59
** FATAL ERROR: -seed dataset time series length 1 doesn't match -input 198
** Program compile date = Jul  3 2019

I know there are 198 time series in my .1D file, so I've transposed the .1D dataset (using 1dtranspose) and tried it again, but then I got:

** FATAL ERROR: -seed dataset doesn't match -input dataset in space

Any suggestions from here?

Thank you.