I assume that you pumped hard a couple of times with the bleeder closed to close the caliper?
Sounds like an air bubble somewhere in the system.
Cure: (sometimes) push pistons back into caliper as far as possible. Be careful and make sure that the reservoir does not overflow. This usually sorts out bubbles in the master cylinder.
Keep on bleeding and topping up until you get pressure. It can take quite a while to bleed air out of a brake by pumping with the master cylinder. Lots easier and quicker with a vacuum bleeder.
If bleeding does not help your master cylinder seal might be shot.