I've created 2 plugins named Plugin 1 and Plugin 2, and it works:
<?php
/*
Plugin Name: Plugin 1
Plugin URI: https://giga.ai
Description: Test Plugin 1
Version: 0.1
Author: Tan Nguyen
Author URI: https://giga.ai
License: GPL2+
*/
if( ! class_exists( 'MB_Conditional_Logic' ) )
include plugin_dir_path( __FILE__ ) . 'meta-box-conditional-logic/meta-box-conditional-logic.php';
Can you please check if another locations has included this plugin? Or please check your hosting environment.
Cheers!