Adding some more info to this. It seems like this error is specific to participant #65. I went back to Setup and re-ran the Setup and Denoising steps for this participant, and yet when I go to first-level analysis and select any of the ROIs for this participant I get the following error:

ERROR DESCRIPTION:

Error using conn_designmatrix
Mismatch info: Please re-run Setup step
Error in conn (line 7949)
[CONN_h.menus.m_analyses.X,CONN_h.menus.m_analyses.select,CONN_h.menus.m_analyses.Xnames]=conn_designmatrix(CONN_x.Analyses(ianalysis).regressors,CONN_h.menus.m_analyses.X1,[],{nregressors,nview});
CONN21.a
SPM12 + DAiSS DEM FieldMap MEEGtools aal
Matlab v.2022a
project: CONN20.b

Does anyone know what the issue is with this participant?