Letting problem

I’m facing many problems to get house on rent. Eligible to get house including income source and legal documents even getting appointment for viewing (few houses) but didn’t get any positive answers. Mostly whenever I call for house if I see on renting application agencies are telling not available for view let me get your details or call us back. Whenever called them back then will say oh sorry we’re fully booked for viewing. On which base they’re finalizing application I really don’t understand