Okay, we now know that you have pin type glow plugs.

Start by checking for voltage at the glow plugs using a DC voltmeter while someone turns on the ignition switch. If there is voltage on all plugs, test for continuity. If there are any open, replace them especially number one that acts as the temp sensor.

If there is no voltage check the bar shaped fuse under the glow plug cover. It can look good but be cracked and actually open, so check with voltmeter.

Since the above is quick and easy to check, do it first. If you don't find anything wrong, check compression.

Hope this helps,