SumProduct failing after row 4789

Which tab?

To John Toley: Which tab?:

The NormData sheet, Rows 4792 onwards, cells B4792 - F4792, and downwards.

Cutting and pasting back in to each of these cells does seem to make the SumProduct function work, so that would be a work-around temporarily. I left these more or less as-is, so you could see the problem.

You'll see that all the preceding copy-downs up to 4792 worked as expected.