Hi - Your issue looks to be that you are trying to edit a survey that you created in the Survey123 Connect desktop application, but using the web form (Survey123.arcgis.com). This is not currently supported - you will need to make your changes back in Connect.
If you want to add a location horizontal accuracy threshold for any geo-points captured, you can enter a numerical value (the distance threshold) in the body::accuracyThreshold column in the survey's xlsform. Please see the following resource for more information: Geopoints—Survey123 for ArcGIS | ArcGIS