Since you have the injectors out for a cylinder soak. I would do a compression check just before installing the injectors again. The rational being do I have good compression or not and how much if so.

That way if the no start continues you will not have to be guessing about the cause. Or at least poor compression has been either eliminated or still the issue.

A person should be able to borrow or otherwise get a test gauge for little effort. A cheap harbour freight unit for instance. Hopefully the soak does it and low compression from sittting was the cause of the problem.

I would also pull the fuel filter and dump the contents into a clear vessel looking for water when the fuel settles out. This is subjective as I do not know if condensation in your climate is a major problem. As already mentioned use the block heater to increase the rate of the mystery oils activity and pre warm the block before attempting to start after the soak. I would hope in your climate the engine has one. Yet a 240d I purchased years ago that had lived it's whole life in new jersey had none.

You also will want to establish fuel is available at all injectors if still a no start with reasonable compression. Under very low supply pressure there seems to be an indication that only some of the first injector elements in line are fed. General smoking when trying to start does not prove all injection pump elements are supplying fuel.