Import issue with Replication
It turns out that the Import wizard ( because it is considered like a Bulk Insert or BCP ) is disabling replication triggers on the tables they are loading data to, which prevents Merge Replication from detecting new records.

This article: Bulk loading data into a merge replicated table explains this with more details.

One workaround is to use the procedure: sp_addtablecontents after importing data to let the merge replication detect the new rows like the following:

Exec sp_addtabletocontents @table_name = 'Customers'