I've noticed an issue with the web service data source configuration window when using jQuery version 3.5.1 or higher.

When you use the click on the Web Service Data Source from the left side menu it will open the configuration window in which Responding encoding and Data selector fields will be there for the jQuery version 3.3.1.

Now try the same steps with the 3.5.1 jQuery version or higher and those 2 fields won't be there.