If the Laser Calibration does not go well, it will show a Failed on the touchscreen. 

When the problem happens, tap on the Failed button, then slide the lines to the left side and tap on the Save button.

Then the screen will back to the main menu panel. Tap on the Calibration button to try again. If the problem persists, repeat the steps above until the calibration succeeds. 

Or, you may change the Laser height(Focal length for the laser) manually to have a try.

On the touchscreen, tap on Settings > Laser > Adjust Laser Height. Then set the Laser Height to 23mm and then do the Calibration again.

Please contact us at support@snapmaker.com if the above tips can not solve the problem.