Recently we ran into this issue when we wanted to send some instructions to students who are active on the course. We filtered the mailchimp list based on the active status and it worked fine for students who are currently active on their first purchase.
However, it is unable to retrieve the students who have renewed their subscription. In mailchimp Active status column, their status is showing as "Active,Expired". Hence they are neither getting selected when we choose to send any communication to all the students in a particular course whose subscription is still active.
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Please look into this issue urgently and provide a fix.