The customer is using the Identity Portal 14.4 CP2 to run certification campaigns based on the Identity Governance 14.4 CP2.
The customer needs to export the campaign as an Excel file, perform the needed action and then re-import the file:
It turns out that it's not possible to import Excel file (modified or not), and an error is returned.
Release : 14.4 CP2
Issue fixed with DE564118 in 14.4 CP2 and will be fixed by default in 14.5.
Both vApp and Standalone fixes are available.