Try cleaning the the electrical contacts on both the camera mount and lens. Bad electrical contacts would stop it focussing.

As the focus isn't settling it sounds like an issue with the camera, however several possibilities to consider:
1. I'm sure you're not, but are you trying to focus on something like a plain wall that confuses the focussing?
2. Can you focus the lens manually?
3. Something else to check, has the viewfinder diopter setting slider moved making the viewfinder look out of focus?
4. When you take a photograph, even if it looks out of focus in the viewfinder, does it seem OK on the viewing screen? (Presuming it lets you.)
5. What happens in liveview?

When pressing the AF it does the exact same the lens motor just seems to make the focus go in and out trying to focus but won't if you know what I mean.[/quote]Ah, I think we've all misunderstood and thought the AF didn't do anything. So it does, but doesn't select a focus point? Is that right?

Yes, if that focuses the camera the AF is working fine, it is just a setting. Worry about which setting later!

You won both cameras this time so I'll give you your one back from last time.

Had you set the camera to only focus with the back AF button? I've thought the same as you before now and that was the reason.

Only on the mark up.

Was it a 645D or a 645Z ?

Thanks for the clarification.

Guess this might be becoming a collector's item now, a Samsung GX-1S (wrongly listed as a GX-15) for £50.

Its at Cash Converters Wallasey.
https://webshop.cashconverters.co.uk/auction-item/1441197/samsung-gx15-body-only...

(Not sure why they couldn't take the picture the right way round, perhaps they should use it themselves!)

2006 ePhotozine review: https://www.ephotozine.com/article/samsung-gx-1s-digital-slr-review-4331

I believe its a rebadged K-10D, is that right? (Apparently not! An istDS - see next post; thank you.)
If it was a GX-15 it would be unique, an unlisted variant!