Hi all. The car in question is a 10/04 production date(2005) Honda Accord "LX" 3.0 V6. It has 175k on the odometer.
This car belongs to my buddy who uses it a few times per week to bring the signs and other related stuff he needs to do open houses when selling a home.

He Amazon bought a replacement plastic case housing for his ONE AND ONLY ignition key and placed the key and chip contents from his original key into this after market key housing. Now his car only cranks with no sign of it catching at all.
The green key mil flashes on the dash.
The key buttons DO UNLOCK & LOCK THE DOORS.

I Google searched to find the location of the IMMOBILIZER FUSE (surprisingly & Frustratingly) with NO success.
PLEASE ANSWER THESE 3 QUESTIONS: #1 Whitch fuse box has the immobilizer fuse in it?
The one under the hood OR the one inside the car on the driver's kick panel by the hood latch?
#2 what is the number for the slot that the immobilizer fuse is positioned in said fuse box? #3 What size FUSE does the immobilizer have?

Im trying not to have to check every fuse...none of the schematics I looked at listed anything resembling "immobilizer"
I appreciate the effort those answering will expend.

 

The fuse that powers the immobilizer is the #7 10A fuse in the fuse box under the driver's dash. It might be called multiplex control unit (MICU) or something else as it powers serveral items.

The immobilizer is just an antenna that picks up the signal/code from the key and sends the code to the PCM. If the code is registered in the PCM, the PCM will allow the car to start. EDIT: I suspect pulling that fuse to "reset the immobilizer" will not solve your problem as the codes are stored permanently in the PCM. Even pulling the PCM fuses won't erase the key codes either.

The green key flashing means the car is not recognizing the key as registered. Since you friend transferred the key internals to a new housing, they either didn't transfer the transponder or it got damaged when moving. I suspect the immobilizer antenna near the key is working properly and not seeing the transponder in the key.

When transferring to a new housing, the metal key, the remote circuit board/buttons, and the transponder need to be transferred. The remote to lock/unlock and transponder for the immobilizer are two separate components. They work thorugh different systems and are not related. The remote not working doesn't mean the immobilizer is not working.

Here are a few videos on transferring the key to a new housing. Have your friend watch and make sure they did the transfer properly, as I suspect this is the issue.

 

Thank you for the very susinct answers. I will use the information you provided to look at the fuse and the key after a deeper questioning of my friend about what he did or didn't do regarding his key.

I will post when I either have learned what the failure is or if I need to get more direction. I dont leave people who help and others who learn from these posts wondering what the outcome was.

 

So you, PAhonda are/were correct!!!. My friend the realtor DID NOT transfer the chip from the old broken key case to this replacement case. That is the only reason this Accord wouldnt fire up.

My 2003 "EX" Pilot key didn't have remote locking door or alarm buttons so I was unaware about that type of key.
Finding the solution lead me in a wrong direction.because my Google searches provided information that seemed relevant to fix the issue but really wasn't and actually complicated and created extra steps to FINALLY SUCCESSFULLY resolve the non cooperative immobilizer issue.

The Google search that lead me astray had me belive I had to have the system "re-see the chip"
To do this one of the steps it suggested was to remove both battery cables and touch them together to discharge the system. The only thing that accomplished was to loose radio presets AND ENGAGE THE SHIFT LOCK.

With the shift lock engaged his EXTRA key that was ONLY a BASIC CHIP KEY This BASIC KEY has that has No buttons to remotely operate the alarm or door locks wouldnt operate this cars ignition. I jumped to the conclusion he had given me a key from a previous Honda he had. I went no further checking why it didn't operate his ignition. My friend was at work doing an open house so I couldn't grill him for answers.

When we finally spoke to each other, II mentioned to him that he needs to stop abusing this car. The coolant is low,the oil is black, brake fluid is low and dirty. Additionally the positive battery terminal is worn/ stretched to the point that I just gave it a thumb/index finger twist to remove it from the battery post.

When I mentioned the battery cable to him he knew that the switch for the shift lock would need to be dealt with from prior episodes. He reset the shift lock,and HIS EXTRA BASIC key turned and started his car.

 

I ran into fuse-box confusion on another car and ended up using https://fubox.net/audi/a6-2026-2027/#Fuse_Box_Location , which made it way easier to spot the right panel and fuse number. For your Accord, once you shift your focus to the under-dash fuse box on the driver’s side and match the number on the fuse cover, the seat fuse usually pops right out.