G540 input 1 not working !

[Action-KAT]

Hi all
Has anyone any ideas why I would lose one of the inputs on a Gecko G540.

I have never used the input until now trying the Autozero setup.
I have a good earth at my spindle end so connected up a
feed from input 1 to a metal plate for a zero tool.
Never got it working found it never lit up on the diagnostics page.

On back tracking I swapped over a working home switch wire from input 2 & tried the switch but didn't work.
rewired my probe into input 2 now the zero tool works fine.

So looks like a dodgy input, Is this something that is easily fixed like a fuse or something or have I got to send it back ?

I have my first paying job & don't want to not do it.

any help would be of great