#IND means that the result is indeterminate. Most likely based on this operation it is due to dividing by 0.

Looking at the formula for correlation, this could be because the standard deviation of asset 1 or asset 2 is 0 or that the series themselves are empty.

I'm going to take a guess. Can you confirm that the length of the two series is the same? Perhaps there is an issue with how correlation calculations are figured when one series is of a different length than an other series?