The key to making this work is adding the Populate List From Array behavior to the onLoad event of the body tag.
In the tag selector, select the body tab, then on the bindings panel, click the plus button and select WA Dynamic Dropdowns -> Populate List From Array.
Select the correct array for the first child list, set the Source list to the Parent list, and set the target List to the first child list.
This step will populate the child list with the correct selections based on the parent list.
Now add the Set Selected in List behavior. On the bindings tab, click the plus button and select WA Dynamic Dropdowns -> Set Selected in List. Set the target list to the first child list. Click the lightning bolt next to value and select the corresponding column from the recordset.
If you have other child lists, you will need to repeat the steps, add the Populate list from array behavior, then the Set Selected In List behavior.
If you continue to have problems, please post a link to your page. you can temporarily remove the update button so it wont work.