The settings API can be puzzling 😉
Replace:
do_settings_sections( 'ia_section_id' );
with
do_settings_sections( 'srchild' );
to display your defined settings section.
The general usage is:
do_settings_sections( $page );
where:
$page(string) (required)
The slug name of the page whose settings
sections you want to output. This should match the page name used in
add_settings_section().
Default: None
according to the Codex (here).