"… was taken out"
A field the pivot used is no longer there for you, so it left the pivot — and the screen says which.
Why a field leaves a pivot
- You chose another Entity with Change: the pivot keeps the fields that Entity has too, and the others are taken out.
- You chose another view under Read through: a field the view does not have is taken out.
- You unticked a related entity: its fields leave the list and the pivot.
- You opened an analysis someone shared: a field you may not read is left out for you.
- The field was removed from the Entity, or a domain view now withholds it.
The line at the bottom of the screen names each field taken out and where it stood. The pivot's other fields are as they were; Undo steps back where the change was yours.