Nozzles on the Isis One may occasionally clog, and are easily replaced. Two spares are included with the printer, more may be purchased. You'll need vice grips and an adjustable wrench. This operation must be done with the extruder hot. Be very careful not to burn your fingers!

1. Make sure the nozzle is actually the culprit.
2. Preheat the nozzle in question. On the LCD console, select Prepare > Preheat PLA to heat the left extruder, or Prepare > Preheat PLA + soluble to heat the right one.
3. Secure the heater block in the vice grips, making sure not to use enough force to harm it or its wiring. Don't let it turn from this position, or you'll loosen the locking nut that holds the barrel at the correct height.
4. Unscrew the old nozzle with the wrench, holding the vice grips stationary with the other hand.
5. Start the new nozzle into its threads by hand, taking care not to get burned.
6. Tighten the new nozzle with the wrench. Don't overdo it.

Hopefully, you've managed to do this without loosening the locking nut that holds the barrel at the correct level. If you accidentally budged it, you'll need to re-level your nozzles and tighten it down again.