Problem experienced:

 

Cannot Sign In to Microsoft Profile - Login wobbler screen launches, but never prompted for username, password, authentication details, etc.

 

Problem experienced on Child profile where Minecraft / Microsoft login previously worked.

 

Troubleshooting steps taken:

 

 

Confirmed that sign-in is possible on adult profile with adult's Microsoft/Mojang Minecraft account.

 

Confirming app permissions in FireOS as having Storage and Contact permissions granted; Problem persisted.

 

Confirmed that sign-in is possible on adult profile with Microsoft/Mojang Minecraft account on Minecraft app on adult's Kindle profile.

 

Downloaded and shared XBOX app to child profile; Confirmed that child's Microsoft account could login to XBOX app while on child's Kindle Profile.

 

Launched Minecraft app on child's Kindle profile subsequent to signing in / authenticating to XBOX app on child's Kindle profile; Problem persisted.

 

Uninstalled and reinstalled Minecraft app for all users of device; Problem persisted.

 

Confirmed that sign-in is possible on adult profile with adult's Microsoft/Mojang Minecraft account.

 

Cleared app data and cache for Minecraft app for all users of device; Problem persisted.

 

Confirmed that sign-in is possible on adult profile with adult's Microsoft/Mojang Minecraft account.

 

Cleared app data and cache for Minecraft app for all users of device, uninstalled and reinstalled minecraft app for all users of device; Problem persisted.

 

Confirmed that sign-in is possible on adult profile with adult's Microsoft/Mojang Minecraft account.

 

Performed factory reset of device, re-downloaded Minecraft app, confirmed that Storage and Contacts permissions were authorised for app, re-shared Minecraft app to previously working child profile; Problem persisted.

 

Confirmed that sign-in is possible on adult profile with adult's Microsoft/Mojang Minecraft account.

 

Created entirely new child account for testing purposes; confirmed app permissions for Minecraft app had Storage and Contacts authorised; Shared Minecraft app to entirely new child account; Problem persisted.

 

Downloaded and shared XBOX app to novel child profile created for testing purposes; Confirmed that child's Microsoft account could login to XBOX app while on novel child profile created for testing purposes.

 

Launched Minecraft app on novel child profile created for testing purposes, subsequent to signing in / authenticating to XBOX app on novel child profile created for testing purposes; Problem persisted.

 

Confirmed that sign-in is possible on adult profile with adult's Microsoft/Mojang Minecraft account.

 

Conclusion: Minecraft app v1.17.41 on kindle FireOS 7.3.2.2, when shared to a child profile, is unable to sign in to any Microsoft accounts / encounters Pufferfish error.