Family Sharing Approval of App keeps Looping

I have my son and daughter setup for Family Sharing. My son has requested for two apps from his iMac (OS 10.10). On My iMac (also OS 10.10) I have selected one notification and have hit "APPROVE' button. It prompts me to sign in to purchase the app (Although it is a FREE app $0.00) and already has my ICLOUD username defaulted in grey, but prompts for ICLOUD password. I enter this and select OK - it keeps repeating this prompting for the password.

I have confirmed I have the correct password by logging into he accounts section of my ICLOUD account via System Preferences.

I have tried the 2nd notification, and also asked him to send a new one (third) request through - but the same 'looping' upon selecting APPROVE/DECLINE occurs.

Per above, I have also attempted to DECLINE the request, but it also prompts for my ICLOUD Password repeatedly.