No start?

Hello, if it will crank over but not start with starting fluid you need to check to see if it has Ignition spark, when it gets real cold sensors such as the crankshaft position sensor can fail, and the ignition coils will not fire without a crankshaft signal. Does the Tachometer move while cranking? And where did you spray the starting fluid? and did you only try it once? It takes a lot more fuel to start a cold engine than a hot engine, especially at only 25 degrees. If you do have spark from the ignition coils you may need to try more starting fluid and spray it directly into the intake manifold and then try cranking it over. Pull off the Brake Booster hose and spray into the intake manifold through that opening, then put the hose back on.

https://www.2carpros.com/articles/how-to-check-for-ignition-spark

The Brake Booster hose runs to the Brake Booster that the Brake Master Cylinder is attached to. Below is a diagram of the Brake Master Cylinder. The Hose circled in green, follow that to where it attaches to the Intake manifold, and pull it off, spray into there and put the hose back on then try to start it. That way you're getting the starting fluid directly into the Intake valves of the cylinders. Spraying into the air intake hose is not close enough. Or you can take one of the hoses off near the throttle plates, I added a diagram of the Intake manifold. In blue is the throttle plates (throttle body), in green are some of the inlets for different hoses, whatever is easier to get to. That way you get the starting fluid behind the throttle plates and into the intake manifold.

If it still doesn't start, check for spark at one of the ignition coils by following the guide above.

Is it turning over very fast, faster than normal? Can you record a video and post it here please? With no Tachometer movement, which means the engine computer is not seeing an rpm signal, does the check engine light come on while cranking as well? Check for spark if you are able. I suspect there will be no spark.

If it is cranking over at its normal speed, then it sounds like you may have had a crankshaft position sensor failure. If it is cranking over extremely fast, much faster than normal, I would suspect a timing chain issue. But due to the cold the crank sensor may have failed. The Tach signal comes from the crankshaft sensor signal to the engine computer, without it you will have no spark and potentially no fuel injector pulse. I will post the location of the sensor for you. These are in the side of the engine block.
The sensor is located on the passenger side of the engine block to the rear. It has a 3 wire connector. It is always a good idea to check to see if there is a voltage feed to the sensor and a good ground. This sensor uses a 5volt Reference feed which is a pink wire with a yellow stripe. The Ground for the sensor is a dark blue wire with a dark green stripe. With the sensor unplugged and using a multimeter you can check across these 2 pins by lightly touching the connector pins with the multimeter leads. With the key in just the On position it should read 5 volts, this is with a basic multimeter set on 20vDC. If you have a video or any questions before testing or replacing the sensor, please just ask.

https://www.2carpros.com/articles/how-to-use-a-voltmeter

https://www.2carpros.com/articles/how-a-crank-shaft-angle-sensor-works

https://www.2carpros.com/articles/symptoms-of-a-bad-crankshaft-sensor

https://www.2carpros.com/articles/crankshaft-angle-sensor-replacement

Did you check for spark? I'll have to look up what the flashing check engine light is all about with no codes. Usually, a flashing check engine light means a catalytic converter damaging misfire, but with a no start is odd. Is the engine turning over faster than normal? You're not getting any no communication messages or no bus messages, are you?
Check to see if you're getting spark. You may want to pull the spark plugs too and see if they're wet with fuel. I'm reading these are known for breaking the timing chains for one bank and not the other.
There is also a Recall on the Battery cable routing. Have you checked all the fuses for any that are open, by a possible short to ground due to this issue. Check all the fuses in the entire vehicle. I'll find all the fuse panel locations. Check these fuse panels for any corrosion, check the connectors and fuse locations. especially the fuse panel on the driver side lower dash. These locations are sometimes exposed to water intrusion.
Also pull out the ASD Relay and the Fuel Pump relay and check for corrosion inside the female pins where these 2 relays sit. The underside of these fuse panels is known for corrosion issues from normal exposure to the elements.

https://www.2carpros.com/articles/how-to-check-for-ignition-spark

https://www.2carpros.com/articles/how-to-check-a-car-fuse

If it's cranking a lot faster than normal, that usually means a loss of compression. You won't hear the rhythmic sound of the cylinders under compression, it will just be a fast-spinning noise, A broken timing chain can do that. But if it was running the day before ok and not the next, the ignition spark needs to be verified first. Depending on the outcome of that test we move to the next. Have you found any blown fuses at all?

https://www.2carpros.com/articles/how-to-check-for-ignition-spark

Okay, sorry things couldn't be easier on you. Let us know what the fault turns out to be. Hope it goes well.