You may need to bleed them again as suggested, or you may need to check the fluid and add some. Fluid should be clear, not milky looking. Milky is because the brakes have gotten moisture into they system. This can happen with brakes on a vehicle just sitting around unused. System is not water tight. If you have milky color fluid, you need to drain the system and refill with new fluid. Then do the bleeding of brakes again. Watery fluid left in the brake system will cause detrioration of the parts and seals.
You need to find out who made the brakes, so you can determine if you need old style fluid or newer types. Fluids are NOT interchangable, wrong kind will eat those seals because they are not made to withstand that mix of chemicals.