If I understand your question correctly you're trying to filter the content on Dashboard B using a URL action on Dashboard A and then applying dimension filters on already filtered Dashboard B correct? If your filters are set to 'All values in Hierarchy' or 'Context' or 'Relevant Values' and preceding filters doesn't have anything relevant the dashboard would turn blank. Consider this example, I have two countries Canada and USA. Using URL I passed Canada as my filter values to next dashboard, so in my dashboard B I see Canadian states but in dimensions filter I'm selecting Texas state then it would turn blank. Make sure you're showing all values when clearing filters, have filters applied to worksheets, etc.,
Hope this helps. If not, please attach a packaged workbook so it's easy to troubleshoot.