Hi,
Can you also make sure, you are re-importing the leads in the same environment?
If you exported the file from Production, updated the new field, and trying to import it in Staging, it won't work.
Because one of the hidden columns (in excel file) has GUID of the Lead records and this GUID is different in each environment.
If you need to test it, you should export this data from Staging and re-import in staging.
If it works fine, you have to do the same exercise by exporting data from Production.
Best,
Wahaj
(if it helps, mark it verified)
