The strange thing is that usually the first install or two will work on any new machine but then it suddenly won't. I had this experience on QEMU 2.13 on a different machine. There is something finicky or buggy about the CUCM installer even when choosing the same virtual hardware specs.
QEMU PC emulator version 0.12.1 (qemu-kvm-0.12.1.2-2.506.el6_10.1), Copyright (c) 2003-2008 Fabrice Bellard
pxe-32 tftp open timeout
The solution was to enable tftp in xinetd with "chkconfig tftp on".
See the troubleshooting below:
NetworkManager 0:off 1:off 2:off 3:off 4:off 5:off 6:off