We have installed a GeoTrust True BusinessID Wildcard certificate on a FileMaker Server 16, single machine deployment, running on Windows Server 2012.
While this certificate gives the green lock and no complaints when used with FileMaker Server 15 - in FileMaker Server 16 the connection is described as not secure. See attached screen shots.
P.S. When browsing to the same machine, Google Chrome tells me the connection is secure.
FileMaker 15 Certified Developer
FileMaker Business Alliance Platinum Member
Square Moon AB
Norra Vallgatan 18
SE-21125, Malmö, Sweden