I have seen this exception in hats trace file (you get it with hats admin console):

Exception = com.ibm.hats.runtime.connmgr.RteException: HPS5109 Hostname [your_host_name]:2809 cannot be resolved. The default port for the RMI connector maybe wrong for your environment.
Look to the end of system.out log file of your server. There you should find a line like this:

ADMC0026I: RMI Connector available at port 2812

The port may be another, this is often the case for test environments. To make HATS work do the following:

There is a runtime.properties file inside your application.ear. There you can set adminPortNum to the port of your servers RMI connector or you go the HATS admin console ‘Getting Started’ -> ‘Management Scope’ where you can set it, too.