dar501
I don't subscribe to NFL+ but from the website looks like the 6.99 offer is limited to phones and tablets for live local and Playoff/Superbowl Games.
Looks like NFL Network, Live Game Audio, Live on-demand and Offseason, and "more" (?) is available to watch on TV, PC, phones, and tablets.
https://www.nfl.com/plus/learn-more (Scroll down the page to "Have Questions?")
The link above was included in the info from the NFL+ channel/app in the online Roku Channel Store. https://channelstore.roku.com/details/b8741c391c59c1dda457073d3295b555/nfl
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A bit confusing, but from the page above, live games can only be viewed on mobile devices. You can try casting these to your Roku from your mobile device.
Otherwise, try contacting NFL+ at support@nfl.com and Roku Billing at https://support.roku.com/contactus (select Accounts, Payments, and Subscriptions). Hopefully, one of these can resolve it for you.
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A bit of friendly advice. Need to really read the fine print and take a few minutes to carefully look at the terms for subscription channels. These services are in the business of getting people to sign up with often confusing marketing and generally not too willing to offer refunds.