GFI's have a line and a load connection. Switch off the breaker for the circuit. Start with the outlet closest to the breaker panel and disconnect the wires on the load side. Turn the breaker back on and see if gfi resets. If it does you know the problem lies further down the circuit. Reconnect the load side and go to the next outlet and repeat by disconnecting the load side. process of elimination. Try to isolate the fault. Hope this helps.
You mentioned you replaced the gfi's...you are aware that the wires (line and load) cannot be switched?
