Fix image not upload in WordPress

functions.php

<?php

// Error while uploading image: The server cannot process the image. This can happen if the server is busy or does not have enough resouces to complete the task.
// Error (Vietnamese): Máy chủ không thể xử lý hình ảnh.

function codetot_image_editor_default_to_gd_library( $editors ) {
    $gd_editor = 'WP_Image_Editor_GD';
    $editors = array_diff( $editors, array( $gd_editor ) );
    array_unshift( $editors, $gd_editor );
    return $editors;
}

add_filter( 'wp_image_editors', 'codetot_image_editor_default_to_gd_library' );