Netflix extra member slot not working

Whenever my partner tries to sign up with an extra member slot on Netflix it completely kicks me out of the household, she has tried on her phone and tv and for some reason every time she signs in it signs her into her phone only and then kicks me out of the household but I'm paying for the extra slot and the actual subscription. What does she need to do set up? We tried signing into the slot with password, qr code, and link but the extra slot never gets used. What is the step by step process to fully set up the extra member slot?