Did you add an external diode across the PFET? The diode shown on the data sheet is built inside the PFET; no external diode should be wired across the PFET.
Wire a diode across the load being switched if it is inductive, like a motor, relay, or solenoid; diode cathode to PFET drain, and diode anode to Gnd.
In the diagram of post #2, the resistor from gate to source is 2.2K.
Measured with respect to Gnd (0V):
What is the PFET gate voltage when the input is 0V?
What is the PFET gate voltage when the input is +5V?
What is the PFET drain voltage when the input is 0V?
What is the PFET drain voltage when the input is +5V?
What is the load?
What is the load's resistance measured with an Ohmmeter?