You may want to carefully check your SI (signal integrity) with the LCD module between the two flavors of the MCU. Different technology parts are going to have different rise and fall times of signals. There is also likely to be different signal propagation delays out the pins relative to the clock or crystal signal provided. You need to check with an oscilloscope to ensure that signals all look good and are not ringing or somehow inhibited from achieving good valid logic levels.

You may very well have both MCUs running just fine but have serious SI issues with one of the two with respect to being able to "talk" to the LCD module. Check with the oscilloscope to verify that the MCU is indeed trying to run. This should be apparent via the LCD handshake signals being present on the port pins.

Different MCUs can also exhibit differing behavior with regard to their XTAL1 and XTAL2 pins and the crystal circuitry connected there. Maybe one MCU is just plain failing to oscillate. This is also something to check with the oscilloscope.

Michael Karas