Is your Dolphin Commander new, used, or heavily worn?
If it is new, try adjusting the floats on the handle to a different position and see if that helps it climb better as well as leave it in the pool for about 15 minutes before actually starting it.
If its not new, call 888-DOLPHIN for help troubleshooting the issue. I have a real deep end that has over 6 feet of full vertical wall which my Dolphin climbs just fine. In fact it climbs several inches above the water line to clean what would be the tile line above the water line in a concrete pool.