Disappearing Data when duplicating text

[MCB123x]

Hello,

I'm using this formula =IFERROR(INDEX(JN,MATCH(0,COUNTIF(JN,"<"&JN)-SUM(COUNTIF(JN,C$7:C9)),0)),"") which pulls a list from a column and puts it in another column, however as soon as I enter a duplicate name/word, it disappears from the list and leaves a blank cell. If this is repeated other names drop off from the pulled list. IDK what is happening.

Any help will do. Thank you.

 

[MCB123x]

That worked a treat. Many thanks.