For people facing the same issue, resolution is probably that in LBWE transaction, the corresponding extractor is marked as Inactive.
This modification is stored in a Customizing Transport. You have to activate it.
if you do it in a Development Mandant but test in an another, you have to transport the modification in the other mandants using SCC1 transaction (from the target mandant, you specify the Customizing Transport)
Hope that helps !