140F is 60C which is very low. Your thermostat is worn and that will make regens not happen. Too low temperatures also wear your glow plugs out as they stay on below 75 C

The dealers are idiots because they won't see a problem because their retarded software doesn't see it as a problem. The stupid car doesn't have a proper algorithm to see that a car that doesn't hit 70C+after a long period as an issue... you would think those idiots would watch for that but they only care about passing the short warranty period. Plus we don't have a freaking temperature gauge, so nobody knows until bigger issues crop up!
Garbage in, garbage out.

Fix the thermostat (waterpump too, not much more and it's on the same spot so labor) and then get it past 70 C/160F and if it doesn't regen, then look at the threads for the trick, which doesn't need Carly iirc.
You can see when a regen is happening by watching the exhaust gas temperature, or EGT in your obd scanner.

F to C. F-32, take that divide it by 1.8
C to F, Cx1.8, add 32 to that number