this sign means a closed tube line. It happens when the pressure in the syringe increases over the settings. Possible reasons and solutions:
1) clogged needle or squeezed tube > clean the needle or release the tube
2) weak pressure settings > increase the pressure level - "<<<P"
3) not enough energy for the drive movement due to an internal problem > perform the repair and calibration (authorized service needed)
Hope for success!
Greetings to India