Sorry.
Please note, it is starting. The best way to describe your problem is, it won't keep running.
It is most likely a fuel issue.
You can test it by opening the hood, open the air cleaner, and spray some WD-40 in to the intake when it tries to quit running. If you can keep it running on the WD-40, but it stop as soon as you quit spraying, it's a fuel problem.
You may have gelled fuel. Get some Power Service 911, and add it to the fuel tank. (Everyone should keep a bottle of this on hand).
You can also put an electric heater under the tractor, and a trap over the top of the tractor to warm it up.
Winter starting requires more glow plug time. What you are using is fine in warm weather. But, when it's cold, you need to them more time to heat up. However, that's not your problem here.
Hope you get it worked out.