All I can think of is that for the ACS 5 year 2020 files they are not presenting data for single parents with children in DP02 anymore.
You can get similar data in B09005 (counts of children) which may serve your purpose.
Also try:
B17012 POVERTY STATUS IN THE PAST 12 MONTHS OF FAMILIES BY HOUSEHOLD TYPE BY NUMBER OF RELATED CHILDREN UNDER 18 YEARS
You will need to add up over several categories. The universe for this table is "Families" If you need the count for "households -- non-families" i.e. people living alone without children you will need to get the extra counts from another table.