The beta program is over long time ago. Because the one ui is rolling out to devices the beta program ends. You will have to wait for official update

I guess you have to log out of Netflix on all devices. You Can do it on laptop. Or web browser.Play from laptop anything and then sign in on mobile app again try.Sometimes Netflix app glitch thinks it's a basic plan

I'm using s21 plus 5g but have not received any update

I had this issue before.Possible Solution :1. Clear app data or reinstall app2. Reset network settings

Which phone?