Can you elaborate? Which version of Metabase are you using? Do you mean that new values have been added to your table, but they aren't selectable as options in your filter(s)? If so, do you have the "in-depth analysis" setting turned on in the Admin Panel? Have you tried doing a manual re-sync of your database in the Admin Panel and waited a little while?
In the upcoming version 0.26, we'll be including a big overhaul to the way we scan and analyze field values and cache them for filters, so that might address your issue.