When using ServiceNow, you have to select a specific table when using actions such as search, create, update objects for generic objects. Sometimes you may not find your table in the table drop down list. This can also happen when you are configuring your Trigger for new/updated objects.
For example, this is how your drop down could look:
However, should you not be able to find the table you require, you can always toggle the 'Table' option by clicking on the arrow to the right of the name, and select 'Enter custom value', and type in name of actual table in the field. Once you enter the name, click outside the field so that Workato fetches the definition for that table.
Do note that the table has to be it's EXACT internal name, e.g. change_request, and NOT it's label.