Uploaded Contacts show as "unsunscribed"

I am moving my contacts from MailChimp to ActiveCampaign and when I uploaded my list of 24,046 Active Subscribers, 3,638 were automatically listed as “Unsubscribed.” I manually double checked a dozen contacts to make sure they are actually subscribed on MailChimp and they are. How do I fix this?

We’re thrilled to have you with ActiveCampaign! Could you DM me your contact info/activehosted account url, as a solve for this might require our team looking into your account specifically?