Were the brakes bled in this order; 1) furthest from the master cylinder - bleed first, then next closer wheel position - until all four wheels (brake caliper / wheel cylinder) have no more residual air.
Check the brake fluid level in the master cylinder reservoir after each wheel cylinder / caliper is bled, refill the fluid and make sure the master cylinder chamber does not run low or dry.
After each wheel is bled properly - check the brake pressure - you should feel the brakes getting a little firmer each time - with each completed step. Try this brake bleeding approach as your first step.
If there is still a soft brake pedal, then suspect the following; leaking brake component; fitting, line, flexible hose, caliper, wheel cylinder or seal, leaking master cylinder. Check for evidence of brake fluid leakage - monitor the master cylinder fluid level to see if fluid is escaping somewhere in the system. Then, inspect for sign of wet brake fluid at the wheels / caliper / wheel cylinders, along the brake line routing, the flexible brake hoses - all the way to the master cylinder.
If the hydraulic portion of the brake system is OK after all this, then check the brake booster vacuum hose and connection for cracks / damage and leakage.