Ronald from the Google Merchant Center (Base) team reported in a Google Merchant Center Help thread that there is a known issue with FTP uploads.
Specifically, if you are uploading new data feeds via FTP, the data won't show up in the dashboard. If your feeds are less than 20MB, then upload manually, otherwise, you are out of luck.
We've noticed that a few users have reported that data feeds uploaded via FTP are not getting updated in the Google Merchant Center account dashboard. We are currently investigating this issue. In the meantime, if your data feed file size is less than 20 MB, please upload your data feeds manually. We appreciate your patience.
Forum discussion at Google Merchant Center Help.