Can't Sum the Numerical Column


I got strange case, where I used to be able to sum the column contains number which is gotten from formula, but now, it cannot be summed… How can?

I was able to do it before, for example this one :


As you can see above, the rolled up column above was able to be summed before, but when I want to edit and click the drop down menu, the drop downed menu for sum is not appear… How can?

Can you track all the way from columns that are part of your math formula to see if any of them is not a number? I would advise to check specifically for any If-Then-Else or JavaScript columns.

it is a number, for a prove, it is written “SUM” there. How can the “SUM” option disappear from the dropdown menu?

Would there have been any changes at any point that makes the source column not fully a number anymore? That’s the only reason I can think of.