Suggestions: What could we check? What might be wrong? on 1997 Toyota 4Runner

We have owned this car for about 14 years and have not had any problems with the car starting. It was starting and running fine until Friday. I had filled the tank on Wednesday. The temperature went below 0 for 2 days and it was not driven. Monday morning it would not start. Since our battery was pretty old we replaced it. the engine turns over like it wants to start but it doesn't. We sprayed ether into the air filter box and that did not work either. Appreciate any help. Thank you.

We have a computerized Car MD, we plugged it into the car and the computer did not find any problems.

Asked by for the 1997 Toyota 4Runner
Was the old battery cranking the engine over but it would not start or was it the old battery dead? When you replaced the battery did you touch the cables to the wrong battery post at any point? If so you may have a blown
The engine was turning over when we first tried to start thecar before we replaced the battery. I also didn't mention that a couple months ago we had the complete exhaust system replaced including oxygen sensor. We were not having any issues with the car after having this repair until the weather got cold. I'm sure I didn't touch the cables to the wrong battery post, but what fuse can I check to see if that is the problem. Thank you