Problem started once child could not purchase minecoins and parent logged in parent's device with the child's account to make the purchase.
Once purchase was made, logged out child's account from parent's device and re-logged on child's device with child's account.
From that moment onward: child account notifications and invites to play are not being received on child's device however they keep on appearing on parent's device.
Thank you for your report!
Issues such as these are often due to a temporary service outage, and should be back up and working again soon. Please keep an eye out for messages from @MojangStatus on twitter for the latest status updates.
For any issues with your specific account or billing, you will need to contact Minecraft Customer Support directly, who will be able to advise you individually.
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