How can I replace a custom-post-type with a custom post category in permalink without getting a 404 in wordpress? - wordpress

Question

I'm a wordpress newbie. I will try to describe my problem in the clearest way possible.
I'm trying to do two things here:
Remove CPT from a permalink.
Add a custom taxonomy type where it used to be the CPT in the permalink.
Permalinks on site used to be like this:
http://example.com/custom-post-type/post-name
I managed to remove the CPT from the permalink based on this:
how to remove custom post type from wordpress url?
Then I modify my code to add the custom taxonomy type to the permalink to be like this:
http://example.com/post-category/post-name
This is my code:
function remove_cpt_slug( $post_link, $post ) {
if ( 'custom-post-type-name' === $post->post_type && 'publish' === $post->post_status ) {
$post_tags = get_the_terms($post->ID, 'custom-post-type-name-category');
$post_link = str_replace( '/' . $post->post_type . '/', '/' . $post_tags[0]->slug . '/', $post_link );
}
return $post_link;
}
add_filter( 'post_type_link', 'remove_cpt_slug', 10, 2 );
function add_cpt_post_names_to_main_query( $query ) {
// Return if this is not the main query.
if ( ! $query->is_main_query() ) {
return;
}
// Return if this query doesn't match our very specific rewrite rule.
if ( ! isset( $query->query['page'] ) || 2 !== count( $query->query ) ) {
return;
}
// Return if we're not querying based on the post name.
if ( empty( $query->query['name'] ) ) {
return;
}
// Add CPT to the list of post types WP will include when it queries based on the post name.
$query->set( 'post_type', array( 'post', 'page', 'custom-post-type-name' ) );
}
add_action( 'pre_get_posts', 'add_cpt_post_names_to_main_query' );
This worked but now every post from my CPT gives a 404. How can I solve this?