Hello, 2 updates ago, this code was working and I am not certain when it broke, BUT I just checked in the docs and you have the same problem we have.
https://ej2.syncfusion.com/javascript/documentation/pivotview/data-binding/#binding-with-odata-v4-services
The headers appear in the tooltip correctly as column: XXX and the pivot table displays correctly, but the Grand Total column header disappears and shows your first data column header.
EDIT: We just learned that if you add: showGroupingBar: true, then the columns come right back, but if you set it to false, then they disappear again. Definitely an issue here. You can use the code below.
EDIT2: I am guessing this was fixed in https://ej2.syncfusion.com/javascript/documentation/release-notes/19.1.67/#pivot-table but the latest we can download is 19.1.63. Where do we get 19.1.67?
EDIT3: Just realized its available in NuGet for weekly releases. Grabbing now.
EDIT4: Can confirm, 19.1.67 fixes the issue.