Entering the Mammoth is a little tricky. It takes a few attempts from different angles to find the right approach. On infantry that cannot enter vehicles, there are some that cannot drive a vehicle on their own but are able to ride as passengers in the GDI and Nod APCs.
As for the Bug Tracker, it's next on the to-do list of forum fixes. Since the upgrade, some services have been needing updating in order to work with this latest IPB version. Hang tight, and welcome back OrangeP47!