After migrating your subscribers from MailerLite Classic to the New MailerLite, you will see the option to Re-sync.
This option allows you to bring more subscribers over from MailerLite Classic, as this will not happen automatically. If you are still collecting subscribers in your MailerLite Classic account after migrating to the new MailerLite, you can bring over your new subscribers with the following steps:
In the New MailerLite account, navigate to the Account settings tab.
Choose the Migration tab.
Locate the Subscriber migration, and click Re-sync.
Important: Your new MailerLite account will need to be upgraded to a paid plan to migrate more than 1000 subscribers.