Update Post Meta for a logged in user

Question

Welcome to WPSE.

A few problems to note:

$user_id is not defined so your call to wp_get_current_user() is passing a null value as a parameter.

$current_user = wp_get_current_user($user_id);. // $user_id is not defined

wp_get_current_user() does not accept parameters. See the documentation here: https://developer.wordpress.org/reference/functions/wp_get_current_user/
This line $current_user->ID; does nothing. There is no ID method in the WP_User class.

You can simplify that section as follow:

$current_user = wp_get_current_user(); 
$current_user->remove_role( 'subscriber' );
$current_user->add_role( 'editor' );

// Assign the ID from the current WP_User object to a var for use below
$user_id = $current_user->ID;

Regarding post update vs creation, wp_update_post() expects an ID for the post you are updating. You appear to pass the user ID as $my_post['import_id'] which is not valid.

Are you attempting to update the user object or a post with user information?

EDIT: OP wishes to update the meta key/value of each post for the current author.

The code above solves the user role challenge and the following is a model for updating the post meta for each post that specific user has authored.

Note: update_post_meta() needs the post ID, the meta_key (the slug for the field) and the meta_value for each field you are updating.
https://developer.wordpress.org/reference/functions/update_post_meta/

// Create array of arguments for our query
$args = array(
    'author' => $user_id,  // defined above
    'post_status' => 'publish',  // ignore deleted/drafted posts
    'fields' => 'ids'  // we only need the IDs
);

// Query for posts by this author
$author_posts = new WP_Query( $args );

// WP_Query object contains lots of info; we only want the posts which will be an array if IDs based on our fields argument above.
$author_post_ids = $author_posts->posts;  // array of IDs only

// Loop through each post by this author
foreach ( $author_post_ids as $post_id ) {
    // On each loop iteration, update the post meta keys here
    update_post_meta( $post_id, $meta_key, $meta_value );
}

EDIT adding actual meta key and value specifics for OP.

function update_role_and_post( $record ) {

    if ( 'Confirm Premium Account' !== $record->get_form_settings( 'form_name' ) ) {
        return;
    }

    // Update current user role to editor
    $current_user = wp_get_current_user(); 
    $current_user->remove_role( 'subscriber' );
    $current_user->add_role( 'editor' );
    
    // Create array of arguments for our query
    $args = array(
        'author' => $current_user->ID, 
        'post_status' => 'publish', 
        'fields' => 'ids' 
    );
    
    // Query for posts by this author
    $author_posts = new WP_Query( $args );
    
    // Parse the post IDs from the rest of the WP_Query object
    $author_post_ids = $author_posts->posts;
    
    // Loop through each post by this author and update to premium
    foreach ( $author_post_ids as $post_id ) {
        update_post_meta( $post_id, 'subscription', 'premium' );
    }
}

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