taxonomy – templates are not loading

There is no direct template for subcategories/subterms.
both will be accessible in taxonomy.php
I didn’t get what’s your requirement to have a separate page for subcategories/subterms.
but you can handle this on taxonomy.php

if( subcat ){
 // show sub category view
}elseif(parent) {
 // show parent category view 
}

or check this answer more related to your request
Different template for subcategories