Why is the filter button not available?

Filters are only applied when stocks are being displayed in the table (with one exception, explained in the next paragraph). So if you have a parent item such as My Portfolios, Indices, or Sectors selected in the Navigation panel, you will not be able to access the Filter button in the Table’s Actions menu. any filters you have in place are not applied, but they have not been lost; they will be applied again whenever you are again looking at stocks.

Filters are not applied to any tickers in the Quotes Box. If you select ‘Quotes’ in the Navigation panel, the filter button will not be usable.