The trimmer head could be clogged with grass or other debris or simply worn out. You can remove the trimmer head to clean it thoroughly, but you may need to replace it with a new one.
The trimmer line itself could be the wrong size for your trimmer or stuck in the trimmer head. Line that is too thick or too thin for the trimmer head won’t feed properly. You should enter the string trimmer’s full model number in our website search bar to find the correct line for your trimmer.
A trimmer head housing that is cracked chipped or broken could prevent the trimmer line from feeding as well. The housing is relatively inexpensive and usually easy to install.