HBO within TV app not showing up on iPhone

I have the Apple TV app on iPad and iPhone (both at 12.3). I subscribed to HBO within the app. When I try to watch something on HBO on the iPad, the TV app goes right to the selected episode. On the phone, it takes me to a page that says I can watch it on HBO Now or subscribe to HBO directly. When I click on “subscribe to HBO”, it tells me I’m already subscribed. But it gives me no way to actually watch it.

In fact, I subscribed to several channels in the app, and they show up under “My channels” on the iPad; but in the iPhone, the whole “My channels” list is missing. Why the discrepancy? Have tried restarting phone, relaunching app, reviewing list of “connected apps.” As far as I can see, settings and app configurations for iPhone and iPad are identical.