Heat error M999 to restart

I have two problems.
The Printer worked fine but once i wanted to clean the Nozzle.
While cleaning the Nozzle the Thermistor has a circuit to the ground and shows 753C° as temperature.
I fixed this error and now the Thermistor works an shows the room temperature.
But the printer won´t start. Repetier shows the error
Printer stopped due errors. Fix these errors and use M999 to restart. (Temperature is reset. Set before restarting )
How can i fix this problem ?

The other problem is that the Nozzle pulls of the Pla filament from the heatbed when printing.
First it worked very clear but now there is this problem.Someone has some hints and tips for me ?

Thanks for your help :slight_smile:

Disconnect the printer, press the reset button on the motherboard (top-left corner) and then reconnect. Everything should be fine.

As for the nozzle pushing away the material,

When you cleaned the nozzle you probably altered the Z calibration. You will need to perform te Z calibration process again.

You can also use a fine grit (400) piece of sandpaper to roughen up the surface of the bed. This will help the pla to stick better.