Confirmation E-mail not being sent

I’m trying to troubleshoot an issue with the email confirmation when a new user registers.
I have Moderation turned on as Email.
A user registers, and it look OK to them, but the actual email is not sent.
I enabled email logging and confirmed the email is not sent.
The user shows in the system as Pending and if I press “Resend activation” the email is sent and received.
Any idea where I should look for the issue?
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I noted another user posted a similar issue 2 weeks ago – would these be related?
https://wordpress.org/support/topic/resend-activation-doesnt-work-with-email/

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