What HelpDesk plugin are you currently using? and what version of Moodle are you using? The HelpDesk plug in that I'm aware of stopped at version 2.5
There's some suggestions on this thread: https://moodle.org/mod/forum/discuss.php?d=334348
As mentioned there (it's not free, but) you can overlay a 3rd party Help Desk system like ZenDesk, FreshDesk, etc.