Hello, welcome to this project. The purpose of this project is to track updates from the whmcsfull.com site and ensure the latest versions are made available.
I want to emphasize that this project is for educational purposes only. I do not intend to cause any inconvenience or engage in any illegal activities. My sole intention is to provide others with an opportunity to test the software. If you have the means to purchase the software officially, I encourage you to do so.
Feel free to share your ideas or questions; I will respond as soon as possible.
Best regards.

I have reviewed the reported error, and it appears to be related to a compatibility issue between one of the recently installed modules and the current version of WHMCS. The module is attempting to use a function that is not available in the current installation, which is causing the error when accessing the module configuration page.
I recommend temporarily disabling any recently installed addon modules and then re-enabling them one by one. This will allow you to identify which module is causing the conflict.