What happens if a district court provides five alternative bases to deny class certification, and the appellant fails to refute one of those bases in its initial brief to the Eleventh Circuit?

That is exactly what happened in Little v. T-Mobile USA, Inc., 691 F.3d 1302 (11th Cir. 2012). In their Initial Brief, the Appellants (plaintiffs below) failed to address one of the bases presented by the district court for denying class certification. For that reason, the Eleventh Circuit affirmed the denial without the need for addressing the merits of the underlying order.