I'm using an Azure AD B2C policy where I'm requiring users to verify their email addresses with a verification code.
Is there a way to check the activity on whether or not this verification code email was sent to the user that is signing up?
There are no diagnostics around the verification code email. The verification code email should be sent every time as per your policy. You can request a feature for diagnostics or something like that in the Azure AD B2C feedback forum
In some cases, emails will get routed to the user's spam mail or the company might be filtering out the emails completely. If you're seeing users from a given company consistently not receive the email, you should get some confirmation from Microsoft that the email was sent by opening a support ticket.