The issue is most likely that the needle(s) have clogged up. To fix this do the following:

  1. Pause the active bioprinting process.
  2. In the “Utilities” menu, turn off the print head(s).
  3. Remove the cartridge(s) from the print head(s) causing the problems WITHOUT removing the air preassure hose.
  4. Remove the needle of the cartridge(s) and replace it with a new one of the same type.
  5. Carefully place the cartridge(s) back into the print head(s).
  6. Resume the bioprinting process.