Second user unable to pair to Index S2 Smart Scales

My husband has purchased the Index S2 Smart Scales. He has connected and invited me as a second user. I have accepted the invitation, however, my IOS device will not pair with the Scales. I have tried resetting - the Scales are recognised by my IOS but things proceed no further. I have applied all the troubleshouting suggestions. Very frustrating.
How do I pair my Iphone?