Possible cause:
String is not sitting properly in the spool.
Click on the guide to learn how to wind the spool.
Repeat process with separate piece of line on lower section of SPOOL.
Repeat on the lower section of the SPOOL.
Note: Carefully ensure that the line is neatly coiled on the SPOOL. Failure to do so will impair the efficiency of the automatic line feed.
After you've done this, proceed to install the cap cover.