Community Moderators ensure that conversations are friendly, factual, and on-topic. We're here to answer questions, escalate bugs, and make sure your voice is heard by the larger Fitbit team. Learn more
@Kaam welcome to our Fitbit Community! I'm happy to assist you with your son's account since you are experiencing difficulties to log in his account.
On your son's iPhone, you need to log in with your own email and password on and then you need to switch to kids view so your son can be able to sync his Fitbit Ace.
As a side note, I'd like to share this help article which explains detailed info regarding your inquiry. Also, please visit this help page which contains more information about how to manage your family account.
Let me know if more questions arise! 
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Community Moderators ensure that conversations are friendly, factual, and on-topic. We're here to answer questions, escalate bugs, and make sure your voice is heard by the larger Fitbit team. Learn more
@Kaam I'm sorry for the late response. However, I'm glad I could help.
As a side note, I'd like to invite you to visit our Discussions board where you can share your experiences, meet people and create new topics.
Hope to see you in our Fitbit Community more often!
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