Hi there!
Apologies, but we do not have an option to resend incentive emails to those who haven't confirmed the subscription yet. I can see that it's already been added to our Feature request, and hopefully, soon enough, it will be implemented by our Team.
As for existing subscribers, may we know why you would like them to receive the incentive email as they are already active subscribers? But it would be best if you send an email to help@convertkit.com50 so the team can take a look at your account.
Thank you!