Leave the tension setting as recommended in the manual.
Be sure you are using a needle for machine embroidery.
Use bobbin thread for machine embroidery. Size 60 unless the manual specifies differently.
The top thread should wrap slightly to the back.
Sometimes the slightest amount of lint or a bit of a thread snip can cause problems...turn off the power, remove the throat plate and bobbin case and gently clean with a cotton swap or the brush that came with the machine.....refer to the maintenance section of the manual.