Near the bottom of that page is an I2C scanner. Load and run that sketch. See what address it prints (if any) for your RTC. That at least proves it is alive. It should display the address 0x68 since that is what you are using.
Near the bottom of that page is an I2C scanner. Load and run that sketch. See what address it prints (if any) for your RTC. That at least proves it is alive. It should display the address 0x68 since that is what you are using.