A couple of forum members have reported this across different platforms.
Here's one example thread below.
My Watchlist is present across numerous NOW playback devices.
Only thing you can do is report it to NOW live chat for them to fix the glitch.
I am guessing you have tried adding new content to your My TV Watchlist to see if the Watchlist grid row appears on the NOW App Home screen page.
Hi @schnapps .
Thanks for taking the time to respond.
Yes, I can see my Watchlist and shows when I login to the NowTv website just not on the Firestick or my Samsung Smart TV.
I will try the support team as suggested.