Most likely it is air in the lines. Try bleeding the longest length of the brake line first (this is usually the right rear wheel) then move to the second longest, working your way toward the master cylinder (i.e. RR, PV*, LR, RF, LF).

* On some vehicles, the proportioning valve (PV) must be bled as the second step. Also, on some vehicles, bleeding the RR also bleeds the LR.

Sometimes bleeding a fresh system will take a while. Be patient, also make sure all your new connections are tight.