I have a field called area cleared and another one called area cancelled. The total_area released is area_cleared+area_cancelled. This equation works well when I fill an empty form. Though the inbox I opened the filled form and I tried to change the area_cancelled but the total_area is still the same.
Am using the latest survey123 connect V3.2.196 and survey123 for arcgis V 3.2.265
Can you please provide a copy of your xslx form so we can take a closer look? When you update the value in one of the are input fields, do you see a recalculate green button next to the total area field when editing via Inbox?
I had the same issue with integer fields. I spent days trying to get it to work. The only solution I could find was changing those fields from "Integer" to "Calculate" (which will hide the field in your survey). Then you could display the field(s) in a Web Mapping Application/Dashboard in ArcGIS Online/Portal. As Philip stated, you can also choose select the green calculate button located to the right of your field. However, if the field is set to read only, that button will not display.
Hope this helps,