EF 70-200 F2.8 L IS II USM focus problem

OK, so I bought this a couple of weeks ago from MPB, I was using it today on my R7 and without any warning it stopped being able to auto focus.

I can hear it trying to work, feel the motor operating etc but it won't focus.

I've tried two other lenses on the R7 (18-150 kit lens and my Sigma 150-600 Contemporary) both of which work fine.

I've tried a freshly charged battery in case that lens is a powerhog, no joy.

I tried the 70-200 on my old D100, and it works fine!

I've cleaned contacts, reset auto to manual, checked I'm using the right distance settings etc.

Full disclosure, it IS possible that I have dabbed one of the R7's many buttons by accident and I have changed something without realising, so can I ask you to be gentle, please?

Any suggestions other than send it back to MPB?