Some of the Contacts are not able to subscribe to the Recurring Notifications topics. Click on the buttons "Get messages"/ "Notify me" does not subscribe Contacts to the topics and does not continue the Flow.
We are looking into a number of similar reports at this time.
The issue has already been reported to Meta Support Team. Please check the following links for more information https://developers.facebook.com/community/threads/1830326477309443/
https://developers.facebook.com/support/bugs/629148905618496/?join_id=f20ff0fea637038
We'll get back to you with updates as soon as possible. Please stay tuned!