The covariates are of the format:
Subject Age TT Labels
S08 30 600 S08.rest.3dTcorrMap.z+tlrc.HEAD
S09...

I've also tried:
Subject Age TT Labels
S08 30 600 S08.rest.3dT
S09...

and got:
Analysis_TT_age: 3dttest++ -setA 'S??.rest.3dTcorrMap.z+tlrc.BRIK' -prefix testing -mask clip_group_brainTissueMask_tSNR10_count_no19+tlrc. -covariates covariates_ageTT_no19c.txt
++ 3dttest++: AFNI version=AFNI_16.3.08 (Nov 4 2016) [64-bit]
++ Authored by: Zhark++
++ 123062 voxels in -mask dataset
++ Covariates file: 4 columns, each with 24 rows
+ Covariate column labels: Subject;Age;TT;Labels
+ Found 2 numeric columns: Age TT
+ Found 1 dataset name column: Labels
++ loading covariates
** ERROR: Can't find label 'S08.rest.3dT' in covariates file
** ERROR: Can't find label 'S09.rest.3dT' in covariates file
etc.
Fatal Signal 11 (SIGSEGV) received
THD_delete_3dim_dataset
3dttest++ main
Bottom of Debug Stack
** Command line was:
3dttest++ -setA 'S??.rest.3dTcorrMap.z+tlrc.BRIK' -prefix testing -mask clip_group_brainTissueMask_tSNR10_count_no19+tlrc. -covariates covariates_ageTT_no19c.txt
** AFNI version = AFNI_16.3.08 Compile date = Nov 4 2016
** [[Precompiled binary macosx_10.7_Intel_64: Nov 4 2016]]
** Program Death **
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