Technologically illiterate

I have created a profile for my son to sign on to the Discovery App in order to link his fitness device to his profile. Every time you try to sign on it fails saying username or password is incorrect. When I contacted the first digital help team they advised that I need to reset the password from the website and try a different browser. I have reset the password 20 plus times and used every single browser known and still does not work. I contacted Discovery again today. First digital support said that he cannot sign on to the website or App as he is under 18. I was transferred to Vitality who again said I most just reset his password. Then after another transfer to two different department can I still not sign on to the App or website and YES I have reset the password. I get constant reminders that "Your kid is loosing out on fitness points" yet no one at Discovery can assist to resolve the issue to sign on to the app to link his fitness device. Completely Useless. Thank you for nothing.