Highlight differences doesn't seem to work

[glenviewjeff]

I enabled "highlight differences" but I am seeing no differences highlighted. I tested it across many different images, but no highlighting seems to be shown even though there are obvious differences to an otherwise similar image. (These are document scans.)

[valsaven]

Could you please attach 2 files where this error occurred as an example?

[glenviewjeff]

Sorry, but this was from six months ago. I don't remember the details or where the project files are, etc.