I have tried all the solutions on stackexchange for this issue, but I still cant get it to work. I have a wire segment that I am trying to duplicate along a curve with the Fit curve option. The wire segment has 2 lights bulbs. The wire array ends up looking very distorted and does not fit the work. I tried it with a simple sphere and it works. Turn on sphere and related modifier visibility to see results. Link to my blend file with the wire segment, sphere and curve.
In order do be well-deformed by a curve, an object must have a location of 0.0.0, rotation of 0.0.0 and scale of 1.1.1.
This can be done selecting the mesh and "applying" its loc rot and scale (Ctrl A).
Then you'll have to adjust the modifier's parameters and tweak the Z rotation of the mesh.
your lightbulbs have nonproportional scale and are rotated. i reset the scale to [1,1,1] and rotation to [0,0,0]. then the array offset can be shortened and the lightbulbs scale can be adjusted in editmode (scaled the mesh down and spherized the bulbs again) now your bulbs objectcoordinates are unskewed, and the bulbs have the right size. meaning their modiefers will also be embedded in a proportional scaled objectspace. heres your modified file