Count Disctinct Items by Date in Google Sheets

I'd like to count distinct on column-B.

I'd like to put it on other cells the outcome:

1Jan24 == 32jan24 == 2. and so on

Thanks

Reading from : https://www.ablebits.com/office-addins-blog/count-distinct-unique-values-excel/

I tried :

=IFERROR(ROWS(UNIQUE(FILTER(a2:a9,b2:b9="1-Jan-2024"))),0) 

Ctrl-Shift-Enter

Why is the outcome 0 ?