The safety feature was activated while I was sewing. Now the machine is frozen. Why won't it sew?

As long as the bobbin winder is engaged, the machine will not sew. This is a safety feature.

Montgomery Ward Sewing Machine Instructions eHow

Check the large wheel on the right side of your machine. Is there a smaller wheel inside? On some machines, this is the mechanism that activates/deactivates the bobbin winder. Will that inner wheel turn? If so, check to see if that causes the machine to sew.

Perhaps the buttonhole function has been activated.
You might check out some troubleshooting suggestions:

Why does the electronic beeper beep and the sewing machine won sew Sewing...

https://answers.yahoo.com/question/index?qid=20071003204543AAVNqqH

Singer sewing machine beeps in stead of sew

Frequently Asked Questions Singer Sewing

the machine probably needs to be serviced, there could be an internal problem causing the machine not to sew

If you can, try to remove the needleplate and the bobbin case from the machine. Once the bobbin case is removed, the needle should be free.

Embroidery Problems Brother Sewing Machine

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it's possible that something has broken or come loose inside the machine and the machine needs to be checked..

it sounds like the machine needs to be serviced to see that wrong
with the machine

since the machine is a bernina, the machine probably needs to
be checked at a sewing machine shop, to see why the power
cord won't retract

You might have thread caught in the take-up lever linkage and it has soaked up all the oil my recommendation would be take it to your local dealer

The fact that your machine is turning hard says you still have some thread inside the machine that is binding up and activating the safety device. It must turn easily before it will work properly again.
Sometimes the machine must be disassembled to remove these threads.
sewman7

If you can return the machine and get your money back. this machine is nothing but TROUBLE and will continue to have problems.