GRN-YEL and WHT-BLU is telling you that the wires that connect to this switch are Green with a yellow stripe and White with a blue stripe and the switch number is 54

Makes it easy to confirm the correct wires are connected to the switch.

The snake assembly use a sim roller micro switch (Part #180-5209-00).
I am going to make the assumption you own a Metallica Pro, as the Premium and LE snake assemblies are slightly different with the moveable locking jaw.
See manual page #151 for the details of the assembly.
It is part #3.

You need to further test the switch, before you worry about game wiring.

Remove the balls, and lift the playfield into maintenance position.
Inspect the switch and wires (wiggle them carefully).
Test the micro switch manually with a small piece of wood such as a toothpick in switch test mode.
Do not use things like metal screwdrivers under the playfield when the game is powered on.
The micro switch is likely it is bent out of contact from use.
This is a very common problem that can occur even out of the box.
If it triggers immediately with full pressure, continue below.

Use a micro hex driver set to remove the switch from the assembly.
If you are very careful you may be able to do the procedure below without removing the switch.
There are two screws and small locking plate that secure the switch to the snake mouth bracket assembly.
Use a leaf switch adjustment tool to carefully bend the roller contact upwards, keeping the rear portion of the leaf closest to the switch unchanged.
DO NOT use your fingers to bend the switch.
Reinstall the switch.
This will allow more sensitivity for the switch to properly activate when the ball lands in the snake assembly.

Ensure you do not power down the game with the coin door open, as I do not know if you have an upgraded "Sparky magnet fix" board which corrected a high voltage design problem.
Earlier games can cause the Sparky coil to burn or transistor failure with the coin door open if the game is powered down first.
If you must power the game down, due so with the coin door closed first, even if the playfield is still in maintenance position, to ensure no damage occurs.

In the advent the switch does not work on testing, and the wires are intact, the cause is most likely a failed micro switch or diode, especially if all other switches in the game are working.

I have had multiple issues with the snake and hammer on my game. Looks like the above posted answered it though.

Test wire continuity first to the switch and previous switches using the same wire colors in the switch matrix.
Switches are wired in series, meaning a bad switch "up stream" can effect others.
This will require turning the game OFF, unplugging the switch IDC from the MPU, and using a multimeter between the board and the micro switch, matching wire color to color.

Also check the switch leads with the solder points by *lightly* bending them, including the diode.
Sometimes funky things can happen with wire leads in conjunction with solder, even on brand new games.

Next, you can make a simple bypass jumper "test switch" with alligator test clips to confirm the switch function when the game is ON in test mode.
If the switch wires test good as "closed", you have confirmed the microswitch has failed, and is not related to the MPU board.

Finally, order a new roller micro switch and diode, and replace via soldering.
Most of the time in these cases it is not being caused by an IC error on the MPU, but rather the switch itself, due to the age of the game, and what you stated that all other switches are functioning normally, but you need to WATCH the matrix carefully during switch activations for "ghosting" blips of other switches for dead shorts.

You'll get it, remain hopeful The blackknight has helped me before, and we are lucky to have someone willing to take the time to explain things we may not be familiar with. I like to see threads like this rather than pm s because if ya have a problem down the road, this will come up in a search and help many people. You will get this sorted out.

Wow, I have been doing this wrong for almost 20 years!

I usually check the diode after I'm certain the switch makes that little click sound. With a digital multimeter you can measure the diode. Basically cut one end off and measure it - if you need help with that, you tube is your friend. Really easy to change out a diode. You will need a DMM, a Soldering iron and solder. These are pretty essential tools for a pinball owner so you probably will need them in the future.

I never recommend people using fingers, flat end screwdrivers, or needle nose pliers for micro switch leaf adjustments if you want a clean adjustment with no kinking or potential breakage.
It is harder to control the preciseness of the adjustment as well, if you are not experienced.
If person wants to use their fingers, that is their choice.
Once you own the tools you have them forever, they are not that expensive, and these tools do not normally break under use, unless extremely misused.

I use a full set for every type of possible angle.
You can even make your own in a pinch with a notched popsicle stick or small piece of wooden dowel with a hand file.
I had to do that a couple of times for owners, if I did not have my full tools.
It is still better than using fingers.

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Although clipping a diode lead and testing it independently (while not under any electrical load) is usually accurate, it is not 100%.
Failures still do occur while under operation.
If there was too much solder used which affects the actual testing result on the remaining soldered end of the micro switch, or could effect the actual operation of the diode when the switch is activated.

"Old solder" (greyish, corroded, or "carmelized") that is on game's microswitches is also a culprit of increased electrical resistance, and can result in switch failure, although nothing is wrong.
The same thing applies for old style GI socket bulbs and wiring.
Literally you can polish it in a second with a dremel wire brush, and magically the switch starts working again.

One of the most common early "crib deaths" of diodes is caused by the diode being overheated during initial soldering without use of a heat sink (common during factory installation) or the diode was directly touched by the soldering iron during installation.

This is why I replace both at the same time, although I do always test the diode beforehand prior to installation.
I think I have only had a couple? diodes fail prematurely when replaced simultaneously with a microswitch in nearly 30 years.
It is a simple piece of mind, to not go back and have to do it again.