I have a Now TV account to which I’m logged into on our tv.
I also want to watch on my iPad but when I log in on the iPad using the same details as the ones I use for being logged into on the tv it makes me purchase a new membership.
How do I get round this? Surely it’s one set of log in details to watch on both devices?
Double check you have downloaded the NOW App for the correct region where I have seen UK customers accidentally download from the Republic of Ireland Apps Store and vice versa.
Also if you are using a VPN or outside the country this will also flag up this message on your iPad.
You could also try a fresh NOW App again, then once downloaded power down the iPad (give it a minute or two) then power up the iPad and sign back into the NOW App with your correct NOW TV account login credentials (where I am assuming you have purchased the TV Membership or Memberships directly from NOW themselves and not a third party such has BT TV for example).
Beyond what @schnapps has said:-
You can log in OK on the iPad with those same details?
It’s not that you are trying to use a different Membership, e.g. that you have an Entertainment Membership which you are using on the TV, but you are trying to watch a movie on the iPad, which needs the separate and additional Cinema Membership? Or vice versa?