HELP! Cors multi frequency coil on Minelab Xterra 70

New on the forum but long term detectorist.
Back in the 1980's l started with a a Whites 6000D
Using an Xterra 70 for the last 10 years or so with standard concentric coils.

Done many hours of research on coils and recently purchased a Cors Scout coil multi frequency coil
7.5 kHz/3 kHz

I wanted a more sensitive coil because I've been pulling copper coins out of a little secret area but the silver was very scant which got me thinking.

And this Cors coil has proved itself as I've been digging threepences, sixpences and shillings but the florins were ellluding me until today when l pulled a mint 1943s florin and a 42 shilling out of the same hole.

PROBLEM
It doesn't seem to work on the 3 kHz setting
I've factory reset the machine several times.
Changed the coil settings to cL.(low frequency)
But no matter what metal it doesn't detect anything much outside of 2 to 3 inches.
I contacted the Cors Lab site for advice and because it's a Ukrainian business the reply l think because of the language barrier was to set noise cancelling to zero which l did but with no result.

Hoping someone has had experience with this particular coil detector combinations.

Thanks

Can't help you Thomo but welcome to the forum.
I have found 38 pennies out of a 2 sq m area & wondered why no silvers. Used a x terra 705. Thought my spot was where they gambled or played cards.
Hope you keep digging when you sort coil out.
GR

Xterra 705 with the 18.75 15 inch coil picked up silver's really well..Even the thrips...

Yes Smoky, I have found thrips before but this patch I'm talking about only pennies. It was wishfull thinking that surely there would be silvers there, I've given it a good going over.