When users click the confirmation link in their email, they have to still tick the post and check "Resume" on the subscription page.
This is very confusing, because they are not resuming, it is a new subscription.
Is it possible that when a user clicks the link in the email, it just subscribes them, so they don't have to click any further checkboxes/buttons?
This is the way most double opt-in systems work. After all, you have already ascertained the user wants to subscribe because they've chosen to follow the link in the email.