Replaced my ECM. Still no go.

[twoleos617]

A few months ago my car would start and run intermittently and eventually it lead to just a short crank but no start situation as if the fuel was being turned off and computer cutting the signal. I checked all connections, fuses, starter, and battery. Battery is new and fully charged. Starter was tested OK. Intermittently a key relearn would work but now no longer does. I bought a new key in hopes that I could relearn with it but symptoms remain the same with either key. Replaced the ECM yesterday with one programmed for my VIN. Still symptoms remain the same. I'll try to attach a video showing and attempt to crank but no start situation. The video was from a few weeks ago. But Now, before and after the ECM swap, I get no attempt to crank or start. Just lights And dings. Throughout the entire ordeal from beginning until now, I've never seen the security light on the dash.
Is it possible that an O2 sensor could cause this?

[Fivefingerdeathpunch]

O2 sensor will not cause these problems.

Perhaps it's more wiring related like power and ground.

[twoleos617]

I appreciate the reply. I was fairly certain as well that the O2 sensor would not cause this but thought I'd ask just to be sure. I couldn't get the video loaded but I think my description sums it up. I've checked ground and power connections from the battery terminals to were each line runs and made sure they were clean and tight. I'm pretty lost at this point. Without further advice on troubleshooting I may be forced to take it to the stealership which I really can't afford at this point. Any other suggestions would be greatly appreciated.