Unable to sign-in to Microsoft Defender on Android devices for child accounts

Just ran into this issue now myself, trying to get this installed on both of my daughters phones. Laptop was fine, no issues, but again as others have said the phones are managed via Family Link, and for whatever reason this is being blocked.

A bit disappointed to see no resolution or signs of a fix from MS, and also a complete lack of response beyond the initial 'I am here to help' post.

Could some traction be made on this please? Would like to use it if I can...

I tried this method and can confirm that it works! I can also confirm that the Family Link restriction is causing the error. Following the steps in the linked guide will bypass the restriction.

Please note: On my end, after I re-added the child's Google account, Defender notified me that I needed to re-log in to the child's MS account. For some reason, I had to re-log in a couple of times before it went through, but after that, everything worked fine.

I finally found a solution. Try this;

https://answers.microsoft.com/ja-jp/msoffice/forum/all/google/c4a53798-9d80-4343-af5f-8c6d44c55ef3

Maybe you should try disabling first the Google Family Link temporarily then log in on the Microsoft Defender app on your child's devices then once successfully logged in on the Defender app then re-enable the again the Google Family Link.

If my suggestion above didn't work, I would suggest contacting the developer of the Defender app on the Google Playstore by searching Microsoft Defender from the Playstore and then clicking DEVELOPER CONTACT's email address atpandr@microsoft.com or leave feedback by rating the app.

Hello lespaulio, my name is Emmanuel.

I am so sorry to hear that you are having an issue signing in to your child's account with Microsoft Defender for Android. Kindly uninstall the Microsoft Defender app from the device of your child then go to this link https://aka.ms/AndroidDefender and install it from there then log in with your child's account.

Please also make sure that your child's email address you are trying to log in to is purely associated with the Microsoft Family account. Please check the spelling carefully.

On your child's Android device, please also go to the main SETTINGS > ACCOUNTS AND BACK UP > MANAGE ACCOUNTS > scroll down from the list of accounts that are currently logged in to your child's Android device and look for the Microsoft account and please make sure no Microsoft account is associated with work or school account. If there is, try signing out first from your work or school account on your child's device then log in to Microsoft Defender using your child's Microsoft Family account.

Hope this information can help you.

Let me know if this works for you.