Sorry to hear you are running into issues redeeming your beta code, but where is this at? Are you on the COD WWII beta page? Also, are you logged into your account when you do that and have you made sure that you have your platform (the one you want to redeem the code on) linked to your COD/ATVI account? Let me know. Thanks.
I am having this exact problem. I followed all the steps but it still says "no country slected".