Form only sending from Firefox?

I've created a Chronoforms 7 form here https://www.farmtrak.co.uk/ and although it will send when I use the Firefox browser it won't send when I attempt to use any other browser?
​
Checking the Debug data when the form sends from Firefox I can see
​

[accepted] => Array
                (
                    [1] => true
                    [2] => true
                )

However all other browsers are showing
​

 [pages] => Array
        (
            [requested] => 2
            [default] => 1
            [this] => 1
            [accepted] => Array
                (
                    [1] => true
                )

            [active] => 1
            [tokens] => Array
                (
                    [1] => 675c0705-b34d-4dc0-8c2d-bc56df0857b0
                )

        )

​
I tried setting up a very basic form here https://www.farmtrak.co.uk/test-form (i.e. just a name and submit) but I get the exact same problem?
​
Anybody have any ideas?
​
Many thanks in advance