you can diagnose the problem using FT_prog;
http://www.tiaowiki.com/w/How_to_enable_virtual_COM_port_on_TUMPA
You need to run FT_prog and check if it can find the adapter,
if it cant find the adapter, try replacing USB cable; if still having problems please contact TIAO corp. customer care;
by opening support ticket at
http://www.csbooth.com/helpdesk/