You need to tell the machine to send the video signal out - Usually a Function Key - Hold down Fn and press one of the "F" keys on the top row - it may have a symbol on it to tell you which - do not do it rapidly - give it a few seconds to work - I beileve there will be 3 conditions - Screen only - Screen & External - External only - well I have seen this in the past - yours may be different.
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