Why is my iOptron iEQ45 handset totally blank? SUGGESTIONS?

[SiteMountain]

Just bought a second hand iOptron iEQ45 mount & taken it to my Astro Club to try it out but the handset won't work! It's plugged into the correct port (HBX) but when I turn it on it lights up but no text shows at all, nothing but it does light up so the power is getting to it. There's no other input on the handset for me to have used, & I've waited over 5 minutes for something to happen. ANY IDEAS WHY IT'S BLANK????

[Cornelius Varley]

Did you buy the mount unseen ? Did the previous owner show you the mount in operation ?

[ronin]

What handset is it ?

Seems there are 2.

Does it say 8407 somewhere ?

Did you press Menu when trying to use it?
The manual says: MENU Key: Press “MENU” to enter the Main Menu.

Just wondering if you get nothing until you go into the main menu.