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Check the connection with the Bernina... it may be connected physically, but the computer may not be recognizing the machine as such, perhaps.
Also, try using a different USB cable.
And make sure it is firmly plugged in at both ends (sometimes, with movement of the computer or the connected device, the USB cable may slip loose a bit, enough to interrupt the connection - especially at the connected device end, where the more-like-square plug is less firmly connected in most cases.
Has this hookup of Bernina QE440 to computer, worked previously, with this machine and the current computer?
That the START button flashes, might also mean that the connection is *not* ready, perhaps (...but I offer this thought only in case it might prove useful... not because I am at all sure of it.)
Let me know more about the circumstances of the problem, and the history of this machine and computer, and I will suggest other things to try, as appropriate.