It's best to move fast so you don't get stuck with a product that is defective.
Call Samsung at 1800SAMSUNG in the USA and check Samsung.com for numbers if not USA. Also, here the web page has a chat I find useful to check if a feature has been discontinued.
WatchOn may be one of those apps that ran afoul of patents or court ruilings.
Hi,
Just got a Samsung S4 (Personal choice) and, am trying
to get the "WatchOn" to work.
I got an "Upgrade" message and, trying to do the upgrade
.... it asks me to sign in and, when I try I get :
"The page you requested is invalid"
Any help with this ... please?

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