I get this error, I'm using Ubuntu 20.04.2

ERROR DESCRIPTION:

Unrecognized function or variable 'mysubs_fields'.
Error in cfg_entry (line 108)
[fn, defs] = mysubs_fields;
Error in spm_select (line 119)
frames = cfg_entry;
Error in spm_select (line 110)
spm_select('regfilter');
Error in spm_jobman (line 173)
spm_select('init');
Error in conn_setup_preproc (line 2988)
spm_jobman('initcfg');
Error in conn (line 1143)
ok=conn_setup_preproc('',varargin{2:end});
Error in conn_menumanager (line 121)
feval(CONN_MM.MENU{n0}.callback{n1}{1},CONN_MM.MENU{n0}.callback{n1}{2:end});
CONN20.b
SPM12 + DAiSS DEM FieldMap
Matlab v.2020b
project: CONN20.b
storage: 1659.7Gb available