Whats wrong with the gh710 trimmer

SOURCE: trimmer feed

try trimmer manuals. the spool is probley wond backword .

SOURCE: B & D auto feed string trimmer won't advance string

Is the string spool seated on the rachet correctly? If so and all is well, it is worth noting that these trimmers auto feed fuunction is problematic at best, requiring manually unwinding some line every few minutes as the unit gets older.

SOURCE: auto feed spool doesn't work

You may need to purchase a new spool housing, which may not be too hard to do, if you have one of the name brand trimmers. This replaces the whole mechanism that holds the line, the retaining ring, etc.