Adobe announced back in July that they are going stop distributing and updating Flash Player after December 31, 2020. You can see their announcement here. This will impact the Facebook Join My Mailing List app, and we are hard at work finding a suitable option for our customers. We don't have anything official to announce at this time, but we do have a workaround in place, and I will make sure we send you an email once we do have something official.
To get started, please Create a Lead Generation Landing Page for capturing new sign-ups. More info here.
Now lets make that form available on Facebook! You have options: