New to Forum, Need ECM Advice

Need advice on replacing an ECM: 2005 4Runner, AT, 4.7L
Codes called for replacing O2 sensors, then ecm. All O2 sensors were replaced.
Located remanufactured ecm, installed and flashed ignition key per suggestions by ECM supplier.
Certified locksmith reflashed, then reset by disconnecting battery and leaving key in the on position both for 15 min each. I am now experiencing no dash lights coming on, no engine turn over / no start. (just after installing ecm, engine would turn over and start, but only run for a second or 2).
Prior to changing ecm, no issues other than engine light.
Whats next, I hope I don't have to take to dealership?

 

I am trying to understand after you replaced the O2 sensors why did you replace the ECM?

 

We read codes that indicated the sensors needed replaced in addition to indicated problem with ecm, so we replaced the sensors, then reread codes, which then indicating the ecm had a problem.