IndexOf Always Shows Index Of Game Object As 0

I’m having a strange issue in Unity where I know for a fact the List I am referencing has more than 1 item in it, yet when I do the following:

int _index = InitiativeList.IndexOf(DefendingUnit);

It always returns the index as being 0. I can test this among many different GameObjects in the list, but it always shows as 0.

I’m sure I’m missing something silly here, but I can’t seem to figure this one out.

Any help would be appreciated.

Thanks

Index 0 is the first item in the list