It is because mapping in time tab is not proper this issue came.
Currently it is match names you should change it to periods. Match name works when the excel file time period and anaplan time period format is same (i've used it for only to get data into weeks but for monthly and yearly it's almost period)
So select period then based on your source data u can select either with Pattern with separators (DD-MM-YYYY) or Fixed Position Pattern(DDMMYYYY)
Unfortunately there is no other reason i have why the data is not coming. Just a health check the line item is in grey colour (either Summary or formula then only it's grey),ideally a data column is blue colour. R we trying to import into some formulated column or something?