What is an E7 reading

Customer Support ,,,,

Do you mean it won't stitch or it won't power up

This sounds more like the motor is bound up. The other solutions are, check for thread wrapped around moving parts, any belts that may have become displaced.

check if the foot pedal connect correctly or not change the footpedal if still not working

I use fray check on all my stitches.

Mine was doing the same thing. I called Singer and if the reverse stitch is working fine, it's a problem with the foot pedal. They sent me a new one under warranty. If the reverse stitch is having issues as well, then it could be a problem in the machine itself.

try new thread ?

Generally, it means that the bobbin is too tight in the cavity.

1. Remove the bobbin
2. Try a drop of oil in the bobbin cavity in the machine, using a Q-TIP
3. After applying the oil, use a clean Q-TIP to remove excess oil in the cavity (may need more than one clean Q-TIP).
4. Replace bobbin.

(I'm sure you already tried differenty thread)

Hope this helps!