Unfortunately, more and more post services add Captcha on they tracking sites. If captcha can not be automatically recognized by the program, the user is prompted to enter it manually. At the moment, there are several such services (china, fj_freipost, etc.). So, when you check each track on these services, you will be prompted to enter the captcha manually.
If you do not want to see CAPTCHA pop up window, you have to disable these services in the track properties window.
Also in the App there is the option "Skip services with CAPTCHA", which allows you to disable the poll of the services that require manual enter of CAPTCHA in automatic or manual modes.