By default the Taxonomy mapping uses the ‘name’ of the Taxonomy for matching to your list. If you’re populating the Taxonomy with the Name as the Label and the Term ID as the Value, you need to use the gform_advancedpostcreation_taxonomy_mapping_field filter to change what ‘value’ is used for Taxonomy to create that mapping match.
There are examples on that page for using term_id and for slug.
// Use term_id instead of name to assign the taxonomy
add_filter( 'gform_advancedpostcreation_taxonomy_mapping_field', function( $field, $taxonomy ) {
return 'term_id'; // can also use 'id' or 'ID'
}, 10, 2 );```