The plugin does not ever throw a 502 error, therefore it doesn’t look like your request is reaching the plugin.
You should check intermediate things, like your CDN, .htaccess file, check your access logs, etc.
Can you enable verbose debug output and check if the cron job starts? i.e.
1. Go to Wallets -> Cron job -> Verbose log output (debug) and enable the setting.
2. Check your WordPress debug log. When you trigger the cron link, it should write to the logs:
cron jobs STARTED
cron jobs FINISHED
Do you see the start and finish lines?
If you see only the start but not the finish, please let me know, because the cron jobs are crashing mid way for some reason.
If you do not see the start message, the problem is not with the plugin and you should try configuring your CDN, firewalls, etc.
Let me know please what you find.