Homelite trimmer bolt for shaft is "welded to the shaft

SOURCE: Homelite strin trimmer head wont rotate

The only way to access the bottom of the metal shaft is to break it. This is fused on at the factory. It sounds like your flexshaft has twisted in two. Remove the flex shaft from the engine end and see if it is in one whole piece or is damaged in someway. If it rotates at the top but doesn't rotate at the string head this is probably the problem. However, Homelite no longer offers just the flex shaft for purchase. You would probably have to purchase the shaft and the tube as a unit.
But if you are saying the spool and string is not turning at the bottom it could be that the cup which holds the string has worn and can not longer be turned by the shaft. Replace the cup that holds the string.
Another possibility is that the shaft have moved forward, away from the engine and just need to be jammed back in, and retightened (the handle grip and the boom clamp).

SOURCE: How do you refill the string on the homelite

Is the sting the cutting line at the bottom of the trimmer? If it is pull the spool out. At the bottom of the spool there is an arrow pointing in the direction that the line should be wound. When you first put in the line be sure to place the cutting line in the grove (V shape) and then when you put enough line around the spool. Thread the end of the line thru the hole on the side of the spool. Slide the spool over the shaft of the trimmer and it will click in. When the line is short just tap the spool lightly on the grass and it will feed out more line.
Good Luck.

SOURCE: Homelite curved shaft timmer line problem

It sounds like its a bump feed which they usually are, try turning on the machine and bump the head off the ground. If this fails to work try rewinding the line on tightly and neatly with no parts of the line crossing over as this could knot it. Quick tip most heads have a arrow pointing the direction to wind the line.

Let me know if that works.

SOURCE: Have a Homelite gas trimmer. Cannot remove the

Not sure but have you checked to see if it might be left handed thread

SOURCE: Homelite trimmer UT20832

The gap on my 18 year old Homelite ST-185 is 0.025. Since they are still using simple and reliable magnetos, yours should be the same.