Some of the emails that the Machine Learning for Kids servers try to send do fail. This doesn't happen a lot - there are generally less than 10 failures a day.
I do keep an eye on this, and generally this is because:
- the receiver's email server actively rejects the email
- the receiver's email address doesn't exist
I have searched through these errors for your email address and I don't see any failures in there for you.
This suggests the most likely reason is that it's been swallowed by a spam/junk mail filter on your side - either on the email server by your mail host, or by your email application.
Are you able to check for this on your end?
If not, ultimately if there is anything you are blocked from doing because you can't access emails, then you are welcome to contact me directly/privately and ask me to do something on your behalf.