Some users experience this when the subscription button is thought to be hit twice in quick succession or you have an active subscription. In most cases it has been correctly linked so please try logging out and then back in and testing to see if premium is working for you.
If this hasn’t worked please check to see it hasn’t been linked to an email address previously used for AnimeLab. Please try logging into this account and seeing if the premium has been attached.
If you are unable to find this please check your receipts for AnimeLab through Google Play or email as this will have a GPA number (unique payment ID) that will help us find what account the subscription is linked to. Please send this through to firstname.lastname@example.org and we will be happy to assist.