I have a problem with exporting XLS from Survey123. It is a survey made via Survey123 Connect with XLS forms. When pointing on export tab it will show me this error: "Export capability is missing in the underlying feature service". I believe I should set it in my XLS form, but it's my first form and I cannot figure out what and where to add.
Are you trying to export via AGO or Survey123 website? In either case the ability to export data to other formats should be enabled by default.
Please ensure the following option on the feature layer is enabled in ArcGIS Online: