I have an outlet that has a GFI. In the past the GFI would trip on a regular basis and I would have to push the reset button back in. Now the reset button will not go back in. Do I need to replace the GFI outlet and what was the cause of the constant tripping?

The GFI device is most likely defective now, may have been getting worse with the tripping in the past, assuming no ground fault is the problem..

If a new device continues to trip, there must be a ground fault on the circuit the GFI is protecting. If nothing had been plugged into the GFI, then it may be wired so it is protecting other outlets downstream, this can be confirmed by finding wires connected to the LOAD terminals on the device, leaving the outlet box going onto other outlets.

First replace the device with a new one, taking special care to note exactly which wire is connected to the Line and Load terminals. If the new GFI continues to trip, then the next step will be to learn exactly which outlets are protected by this GFI, and troubleshoot to locate the ground fault.