Are you using the NowTV box in the picture that i posted or a different style box ?
If it's a NowTV Box with the pink NowTV logo on the top casing or there is no NowTV logo on the box top casing then these boxes are not Freeview compatible and you will not receive TV stations such had BBC 1, BBC 2, ITV, etc etc via a TV aerial and you will have to use the Terrestrial Apps such has BBC iPlayer, ITV Hub etc for certain amount of limited channels.
If you are using the same box has the photo with the blue NowTV logo on top of the box casing, then when you plug your TV aerial directly into the back of the television inbuilt TV tuner and do a rescan does BBC 1 and BBC 2 appear on your television screen ?
If you came from BT and you have a BT Youview box, then use the over the air TV channels via the TV aerial and for NowTV access use the NowTV App on the Youview Box (this might be the same for TalkTalk and Plusnet, but i am not one hundred percent sure because if am not familiar with their Youview boxes).
You still haven't confirmed which type of NowTV box you have ?
From the link below, which type of box do you own ?
You also mentioned that your previous box or streaming service had BBC 1 etc, can you provide more information ?
Do you own a BT Youview Box, TalkTalK TV box or Plusnet TV box or something else ?
Re scan of the TV channels just means a retune of the TV channels via your TV set (no point doing this yet until you can confirm all of the above).