How was I meant to receive pioneer Nora at the begging of the game as I never did and is it too late..

Pioneer Nora usually arrives during the introductory tasks that you perform during the first few levels. I can't imagine why you may not have gotten her (unless they have changed it) but if you don't have her then she is still a hero that will appear randomly in hero recruitment. Purples are fairly rare, but she will pop up eventually.

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Actually you already have Nora. The problem is you only have 1 hero slot. If you want to add nora in, you have to removed your current hero. You can remove and placed hero at the world map when you are about to attack something.