[MrRoro]

Is the key fob for 2021 model is able to be programmed manually?

 

[Fummins]

Do you mean without the use of a scan tool? I don't know. One some vehicles if you have 2 working keys, you can program a third by following a series of steps.
I have no idea if the instructions in the link below work or even apply to the nv200, might be worth a try? Or not

https://www.suntrupnissan.com/manufacturer-information/program-nissan-intelligent-key/#:~:text=The%20first%20step%20to%20Nissan,hazard%20lights%20will%20flash%20twice

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I use an autel scanner to program keys for these vans. There's two steps if you have keyless entry, one for the imobilzer part so it'll run and the other programs the keyless entry buttons.

 

[key4car]

You need scanner