Error when georeferencing a section on a line

OliviaDodds

I am attempting to georeference some geophysics data along a line which I have been given the start and end coordinate points for.

After georeferencing and hitting 'save', I get the following error: 'linear space locations: Cannot position image when the Marker Location (X, Y) values have duplicates or lie on a line.'

The section is vertical with two points (green circle and yellow square) and should lie on a line.

I'm some seeking guidance on what i'm doing wrong.