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I have tried to connect the 2 arduinos together
having issues if the device you are trying to communicate with is not on the same voltage level
That would only work if you uploaded a sketch to the second arduino to make it behave as an i2c slave.That could be the problem, yes.You could try connecting the pull-up resistors to 5V, but it could in theory damage the display, so do it at your own risk. Otherwise you could try an i2c level converter module. I've connected similar displays to 5V arduino before with no problem. In think my displays have a regulator built in, so can be powered by 5V, yours may not because it sold for use with pi, which is 3.3V. But I'm pretty sure my modules don't have built-in level converters, and they have always worked fine with 5V arduino and 3.3V arduino.
Even with the slave sketch on the arduino nano, the mega still doesnt find a device with the i2 scanner. There is also no output from the serial monitor on either the mega or the nano.