Urgent issue! Change status: 'consent approved' to 'consent required'

Urgent issue! Change status: 'consent approved' to 'consent required'

I have tried to sent out a 'consent email' to people that I have imported through a CSV file.
Apparently when you import these contacts, they directly get a 'consent approved' status. Therefore I wasn't able to sent out the consent email. Someone told me that you cannot sent a consent mail to people that already have a 'consent approved' tag. 

My question: how can I change the approved status to required status? So I can sent a consent email to my imported contacts? 

Thanks a lot!