Hi, Welcome to JustAnswer.com, I am glad you are here! My name is Eric & I will endeavor to answer your question.
Disconnect the wire to the pushbutton from the circuit board. Let it sit a while to see if it opens on its own without the wiring connected. If it does, you need to replace your circuit board. If not, reconnect the wire to the circuit board and disconnect it from the push button. Now see if the gate opens by itself. If not, rewire to the push button and see if the problem continues. If Yes, replace your push button. If the gate opens by itself with the push button disconnected, replace the wire form the opener to the push button in its entirety. If your wiring is buried or in walls, conduit or otherwise difficult to replace, you may do the test by running new wire right across the drive, swail or yard from the control panel to the push button. Disconnect the old wire and connect the new wire at the circuit board and push button (even though not yet run on the correct path). If the gate works fine and does not open on its own after that, you will have to do a permanent wire replacement.
In the event that you do not possess a copy of your Owners Manual, or just in case you might like to have a copy stored on your hard drive, I have provided the link where you may download a copy of it.
And here is the link to where you may down load the troubleshooting guide.
Please let me know how you fare!