thanks for some reason using the link from the app I got an error when trying to sign into my Samsung account. You link had me sign in first and then input my imei and go from there.
The link worked for me. I'm not going to get the plan personally, but wanted to try it to see if it works, just to confirm.
Make sure you are on the right website for your country. Often Google results go to a specific country version of Samsung (each country seems to handle Care+ differently) but can set cookies defaulting to that country.