A non starter, bit sparse on info, forgive me but please have a go at diagnostics :)

So the bike is stored 20 minutes drive away so forgive me if the info is not complete.

2008 R1200GS. Parked in garage last Sunday week after 200 KM run. Tried to start it after a week, engine does not turn.

Battery is fully charged as per BMW charger. Some clues maybe:

Turn key, dash comes on and dip or main beam (I thought normally only parking light comes on if bike is not running, must check)
I cannot get neutral light on, tried the usual, into first gear back to neutral, check back wheel spinning freely.
Tried with clutch in and side stand up, nada!

A couple of possible red herrings into the mix: I am fortunate to have a near identical bike (2008 R1200GS) and I mistakenly tried the key from this bike in the filler cap... so I am wondering if something funny has gone on with the immobiliser.
There is a new dog at the house that chews everything so I need to have a good look to see if anything is out of place.

So there you have it, I didn't spend long at it yesterday because I was due to meet up for a spin so I jumped on the other bike. I have 911 diag so I guess that is the first port of call but test sequence advice appreciated.

Kill switch

It really is in neutral, not a false one somewhere up the box.

Light switch in main beam position switches on with ignition

Double check battery state - just coz you put it on charge doesn’t mean it’s still ok.

Check battery terminals.

Check the main fuse.

Umm that’s it off the top of my head.

Simple. The neutral light needs to be lit for the engine to turn over. It will turn over if it’s not lit but with the clutch lever pulled in…… if you have tried pulling the clutch in while pressing the starter button ( you haven’t said in your post) and it doesn’t turn over then it’s the clutch bypass/override switch. Which has either failed, or (the most common fault) needs adjustment.

Thanks folks, will report back.

Mine did exactly the same thing, Neutral Switch iirc....

As Steptoe says, the clutch pulled in should allow a start of the bike, such as when stalled in-gear you can quickly pull the clutch in regardless of gear position and restart the engine then quickly ride out of harms way....unless the clutch lever microswitch is out of adjustment (or faulty). There is a tiny allen grub screw that allows you to adjust the clutch lever microswitch into a working position. The range of travel is very sensitive and easily disturbed.

I'm pretty sure my 2009 headlight only comes on once the engine is running, as you stated. Can't check as my bikes split in two at the moment.

If you genuinely can't find neutral its either a mechanical gearbox fault, or more likely the black plastic gear position potentiometer on the back of the gearbox is faulty. They aren't cheap to replace for what the are.

and then I noticed EWS on the display. I think I will start a new thread.