If you're still having this problem, swipe down from the top of the screen and select Storage > Internal Storage > Apps & Games > Minecraft > Permissions and turn on both options (likely only need to enable Storage permission, though).
I'm having the same issue. Tried with both my child's and my parent fire account.
If you're still having this problem, swipe down from the top of the screen and select Storage > Internal Storage > Apps & Games > Minecraft > Permissions and turn on both options (likely only need to enable Storage permission, though).