Formula Won't Copy Down

[pmd]

Hi,

I am using the following IF statement to guide users to complete columns B, D and E so that column R auto-completes:

=IF(OR($B$8="", $D$8="", $E$8=""), "You must enter a CI Name, Tag Number and Serial Number before completing this field","Hardware")

I have tried copying the formula down and using Paste Special but I still get references to the original rows (i.e. Row 8). I have other formulas in the sheet and have tested them in coloumn R and I am able to get them to correspond to the relevant row (e.g Row 26, 27 etc for: =IF(ISBLANK(U26),"",VLOOKUP(U26,ModelManu,2,0))

Have checked cell validation is off, data type etc but nothing seems amiss. Any ideas if it's formula related but this doesn't seem to be a logical root cause..?

Tnx