I am attempting to load an externally generated SVG file into Inkscape and I get a message saying that Inkscape could not load the file but giving no clues as to what might be wrong. A copy of the file is given as an attachment. It is not yet complete. I have no previous experience with Inkscape or with any other graphics program.

I got an error on your file saying the file is empty what could be true with a bite length of just 432.

It's not empty. Just open it in a text editor and fix the code.

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN"
  "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
<svg width="450" height="400" version="1.1"
xmlns="http://www.w3.org/2000/svg">

  <path id="topOfArrow" d="M 100 350 q 250 35 300 0"
stroke="red" fill="none" stroke-width="6"/>
  <path id="bottomOfArrow" d="M 100 370 q 250 -35 300 0"
stroke="red" fill="none" stroke-width="6"/>
</svg>
 

On the basis of what I can see in a text editor of your sample svg file I would not use the program that generated this svg, it is corrupt.

Here are the corrections I made to get it to display: look at the changes within { }

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN"
  "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
{add <}svg width="450" height="400" version="1.1"
xmlns="http://www.w3.org/2000/svg">

  <path id="topOfArrow{replace ¨ with "}{remove comma,} d="M 100 350 q 250 35 300 0"
stroke={replace ¨ with "}red" fill="none" stroke-width="6"/>
  <path id="bottomOfArrow{replace ¨ with"}{remove comma,} d="M 100 370 q 250 -35 300 0"
stroke=[replace ¨ with "}red" fill="none" stroke-width="6"/>
</svg>

Attached is a fixed svg.

I got this error hence my comment:

Polygon

I got this error hence my comment:

In Chrome the error message is more correct.
In addition View page source is an option when you right click the error message.

I‘m just on my iPad right now. 😅