I was able to bypass through fuse box relay to turn the engine, no problem. But even if the car doesn’t recognize the key what should be the state of the dash with the doors unlocked, do you know what needs to light up? If the state is exactly as assumed then I can go buy the start button or try to re-program the FOB. I just don’t know if the wheel lock also locks something on the ECU, in the mechanics manual it says that it does lock and ECU needs to unlock to allow the steering wheel free.
https://cimg4.ibsrv.net/gimg/www.cam...73fb195c1.jpeg
In the tech manual it mentions that why power would not turn on

Toyota says to push the start button and brake pedal to light up the dash.

Is the red security light on the dash blinking? The Toyota security system cuts off power thought to the injectors via the ECU and there was no work around I knew of as in jumping a relay to bypass this. The engine starting should mean the ECU recognizes the key transponder code or it would not start.

This leaves the issue with the steering lock, start button, etc. Here then the key chip link to the ECU seems OK. The FOB signal seems OK as one can unlock the door and trunk with the FOB in hand by grabbing the handle. The ECU would need to recognize the FOB to allow this. I assume its a one size fits all recognition by the ECU to release power to the locks AND engine starting system. Yet no power to the start system.

These leaves the start system. Perhaps a power issue as in dead circuit. Suggest backing up the wiring from the relay you bypassed to find out if the power is OK to battery. Sometimes a high amp fuse say 40A or 100A blows and causes issues. Suppose over time something could corrode a connection or mice eating wiring, etc.

Yes the security light keeps on blinking, shouldn’t it stop once you validate with ECU? If I cant then the connection of start button with FOB is not working

Is the light flashing when the engine is running? If light is flashing then the immoblizer is supposed to activated and engine is supposed to be not able to start but you got it to start.

Have you tried touching the key FOB to the start button? The button has its own FOB "ringer." The ringer picks up the FOB signal.

It appears every device such as the door lock(s), trunk lock, etc has its own ringer that responds to the FOB.

Toyota refers to a switch that can turn off the smart key system located below the steering wheel at the bottom of the instrument panel. If equipped with said switch and off then the smart key system will not work.

my answers with @@@

Don't know and the issue is appears too complicated to diagnose over the internet.

Suggest you consolidate your answers then post at the Toyotanation.com site in the appropriate year Camry section. The website has tens of thousands of members and you should be able to get a better response.

Did the vehicle run when parked? Did someone come along and try to jump start the engine using jumper cables. This can cause fuses to blow! Typically the ECU seldom fails but perhaps the sensor pickup in the smart key button failed. Ebay may have low cost used ones.