Unable to start TEP, TEPS hostname incorrect

I’m trying to start TEP using java webstart.
It works to a certain point then returns the error

Unable to load resource: http://TEPHOSTNAME:1920///cnp/kdh/lib/tep.jnlp

The issue must be that only the short name of TEPS is displayed, that can’t be resolved from the machine where I try to start the TEP.
I tried starting TEP using the FQDN of TEPS and even the IP but the error does not change.
How can I force TEP to use the full name of the TEPS server and not just the shortname.