HS.OpenCellTextUnit returning 0 items

Hi

Can someone tell me why the function below returns a text value:

This_txt = HS.GetCellTextWithLabel("A#DivRec_Int.I#NIT200D.C1#CB_Load.C2#[None].C3#[None].C4#[None]","[Default]")            

WriteToFile (This_txt)

2020/12/08 01:31:58 PM = Hello world

Whilst using the HS.OpenCellTextUnit function returns zero items?

Set CTU = HS.OpenCellTextUnit("","","","")

NumItems = CTU.GetNumItems()

WriteToFile ("Items: " & NumItems)

2020/12/08 01:31:58 PM = Items: 0

This is for HFM 11.1.2.3.

Thank you.

Chris.