Having a quick read of this linked article below it says LG Smart TV's 2015 and onwards with some exclusions, so i am guessing Hayu is not available on all LG inbuilt native NowTV Apps.
Perhaps post back your model number of the LG TV and if another forum member has the exact same model number they could confirm either way if there is a Hayu section on the NowTV App or not.
I own all Panasonic televisions so i wouldn't be able to help any further.
I must admit im finding it increasingly hard to comprehend NowTV's rationale for its appallingly fragmented platforms.
The nowTV offering should be IDENTICAL across any platforms it supports and its fee-paying customers can use.
It is simply not reasonable as consumers to have artificial restrictions placed on us just because of the platform we choose to use. The service is advertised as being available on a platform, and that should be the full service... not a subset depending on what you are viewing it on.
At the moment, Channel selection in the Entertainment Pass, Picture and Sound Quality (boost), and core functionality (watchlist and continue watching) are all sacrificed on one platform or another.
If you want the "full" proper experience then you pretty much have to get the NowTV box or stick... or at least those are the ones where you can 'guarantee' the most complete and up to date experience on offer.
The other platforms are left in the dust.
I think they should have different payment tiers depending on what platform you are using.. if you dont get watchlists, or a full channel selection then you shouldn't pay as much.
OR, as I have noted in the past... rationalise the number of platforms you purport to offer. Get rid of the smartTV apps. If you ONLY offered NowTV via the official Box or stick.. then fine - at least all your customers are getting the same service.
Currently, they are most certainly not.