Could anyone please give me some idea why suddenly, the google checkout button 'went' grey, although it was working previously?
Here is more info:
On test platform, I have installed Google Checkout mod v1.4Beta1; configured it for sandbox; as test-client, I have added items to the cart and checkout with Google Checkout button > was redirected to the GCO website; logged in as a sandbox test-user: all went OK.

I tried a second attempt: in admin>modules>shipping I have disabled some options (Per Item) and enabled other (Per Unit) for further testing purposes. The Store Pickup was enabled in both cases.

After doing so, the GCO button became inactive (greyed out) - I didn't do any other changes, so I wonder what could possibly affect that?

Please help,
Thanks,