I am running several tests in order to import emails into a Zimbra server, using ZCSPSTImportWizard- I guess I worked "by the book", but the checkbox "ignore previously imported items" keeps being greyed out, whatever the test I am running, on three different PCs - anybody has an explanation/ a hint about how to fix it ?

Each time, I run a first test, at the end of which I uncheck the box asking for the logs deletion, then I run my second test - and the checkbox is still greyed out.