@weedeater, EMMA, The stringers head may not have the string wrapped properly onto it. Remove all the string and replace the nylon line with appropriate/compatible line and try. If this does not do the trick disassemble the string spool head and check for dirt/debri(clean head) check for damage, rethread and try. If still no go the head must be damaged/worn and will have to be replaced. If still under warranty, use warranty for repaired/replaced/refund. Below 1st link is a video to show how to restring head on Echo Speed Feed head, 2nd link is for generic type Echo head, 3rd link is Echo SRM-225 Trimmer manual. Good luck. I hope this helped you out, if so let me know by pressing the helpful button.

https://www.youtube.com/watch?v=INyxjCrL...

https://www.hunker.com/12325929/how-to-r...

http://www.echo-usa.com/getattachment/70...