symbol not added to dmg files

[ColinM]

Not recognising Extension dmg
In  Category 'dmg-files' I have used FileZilla to uploaded the 3 files listed below
Wordsmith_1_4w.dmg
Wordsmith_1.4.dmg
Wordsmith_1.4 - Copy.dmg

Checked that in File images/jdownloads/fileimages/flat_1 contains dmg.png  -  dmg.png is also in file images/jdownloads/fileimages/flat_2

Downloads of these were then created using the Control Panel Check Download Area with the 'Full Scan' Option
This created the Downloads OK but there was no icon shown as illustrated in the attached