Based on the fault code, from Evilution:
451 CDI Exhaust Pressure Sensor, SMART β 0061539528 version 1, SMART β 6429050100 version 2
OR...
45bhp CDI EGR Clean
Both require a subscription to read in full. π
What year 451? How many miles? The low compression could be from burned valves in one or more cylinders - a known issue with some 451s/Mitsu engines. Our 2011 got a brand new head at around 32K miles due to burned valves. As to the no start, I'd scan the car for OBD codes and see what pops up - sound like the computer isn't seeing what it needs to allow the start. It's also worthwhile checking the connectors and cables to the starter just in case...
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