I have the same problem happened this week I have to keep removing and downloading app again.
Exactly the same for me. I am very unimpressed with the whole NOW technical offering - login is problamatic and the only way I can see the Ryder Cup is on my smart phone since both TV and Now TV for Mac fail to work.
Not sure if this has been answered &, if it's the right fix.....
BUT, I can't access NOW tv on my tv - through the app - I just get a white screen. So, to fix this scenario - search for Nowtv online& load it from there - it works a treat 😀
Hope this works for you peeps - let me know how it goes 👍
It also works if you search for and launch the app from the Samsung Apps store, instead of the direct from the smarthub. A bit of a pain but it works.
I have also reset the smarthub which also works for a time, but the issue starts to crop again after a short time.