Okay, I see what is going on. Publishing a survey with a repeat group to an existing hosted feature layer will not create a related table for the hosted feature layer because it cannot change the existing schema of the hosted feature layer.
Here are two options you can try:
1) Instead of publishing the survey to an existing hosted feature layer, create a new hosted feature layer when you publish the survey and the new hosted feature layer will have a related table by default since the survey has a repeat group.
2) If you need to use the existing hosted feature layer then you can use ArcGIS Pro to add a table to the hosted feature layer. You can do this by following these steps...
- In ArcGIS Pro, export your hosted feature layer data to a file geodatabase (right click layer>Data>Export Features)
- Add GlobalID field to the data layer inside the file geodatabase (right click data layer inside file geodatabase>Manage>Add GlobalID)
- Create new table in the file geodatabase with any fields your table requires plus a GlobalID and GUID field
- Use the Create Relationship Class Tool with the data layer as the Origin, the table as the Destination, One to Many as the Cardinality, GlobalID as the Primary Key, and GUID as the Foreign Key.
- Finally, in the Share tab of ArcGIS Pro, click the Web Layer dropdown and use the Overwrite Web Layer tool to overwrite your hosted feature layer so it that now includes a related table.