If you're having issues, I can recommend more secure, updated alternatives to 2021 software.
Require a URL, Username, and Password in http://url:port/get.php?username=X&password=Y format.
Many tools from 2021 rely on older security protocols that are likely blocked by modern ISPs and firewalls. Additionally, many IPTV providers updated their API security to block automatic testing tools. To make sure you get the right help, could you tell me: Are you looking to check/test a list, or edit/organize one? Do you need this for Windows, Android, or Linux ?