Singer 7442 the machine doesn't start. Machine beeps when foot pedal is plugged or when back stitch button pressed. The needle moves if I spin the wheel manually

Sound like one or the other of the threads is stuck. Completely un- thread your machine and remove the bobbin. See if the needle moves freely with the machine unthreaded. If it does, carefully rethread the machine and reinsert the bobbin, making sure the bobbin thread is feeding the correct direction. Let us know what happens.

Is this a Singer Fashion Maker Rotomatic 974?
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The beeps usually indicates that your machine is not ready to sew which probably means a function has been left in the activated mode, ie bobbin winder, buttonhole function, etc. . Here are some ideas:

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Please check the Stitch regulator & Presser foot lifter.

sounds like the new top tension dial is not working either
there could be something wrong with the computer part of the machine
is the power cord plugged in correctly?
also is the foot pedal plugged in correctly?
have you had the foot pedal check to see if there is something wrong with it?
I would suggest having the machine check, there are lemons even in sewing
machines

Move bobbin winder to LEFT. Your machine is set to wind a bobbin.
Hope this helps!
Jimmy

Make sure that you pushed the bobbin winder all the way to the left.
Jimmy

Are you sure that you are plugged into a good wall plug and the machine turned on with a stitch pattern selected with a length stitch picked not a 0? If you do not have a manual go to singerco.com and download one for free.

Change to a new needle appropriate for the fabric you will be sewing. Make sure the flat side of the needle shank faces to the back of the sewing machine.

Always thread the machine with the presser foot up as this will "seat" the thread into the tension control.