With twenty (20) of these around the property, something was bound to go wrong. After the second year, five (5) would no longer come on at night. After some diagnostics on the first one, it turned out to be the main "On/Off" switch causing the issue. Bypassing that switch on all five solved the problem.

Supplies

small Phillips screwdriver (2.0mm)

soldering (not required but highly recommended)

shrink tubing (again, not needed, but...)

Step 1: Open the Case

Remove seven (7) screws.

They are small, so have a dish or something to keep them in, so they don't get lost.

NOTE: The case should open with all components on one side. Those components are "slip" fit and will fall out if the case is turned wrong. For this repair, it is easier to keep everything in its place.

Update: 8/17/2022 6:37pm

I just remembered one more light that has not been turning on at night. As I was bringing that light into work on it I realized that the wires to the on/off switch could be accessed without taking the light apart. I just snipped those wires close to the switch, pulled them out to strip, and connect them together. I put a little liquid electric tape on the connection and stuffed it back inside. Perhaps five minutes to complete the whole job!!

Step 2: Bypass the On/off Switch

There is a cover over the back of the on/off switch; it just pops off. Or leave that cover in place and cut the wires leading to the switch. I like the extra inch of wire I get by removing that cover and pulling the wires off the switch.

remove the wires that lead to the on/off switch
strip about 1/4" off both leads
wrap those leads together

This bypasses the on/off switch, leaving them permanently "On." The On/Off switch is only there, so you can turn them off before placing them in storage. The actual On/Off (day/night) function of the light itself is controlled by a photocell in the solar panel

TEST the light

If the On/Off switch was the problem, the light should now function as usual when it gets dark. Move to a shadier location and, if required, block any light reaching the photocell on top of the solar panel (cover the board with your hand). The light should turn on and off based on the amount of light reaching that photocell.

Step 3: Clean It Up and Close the Case

After confirming the light is now functional.

I soldered the connection made in step 2
at a minimum at least secure it with electrical tape
I used heat shrink to cover and protect the connection
Tuck and hide the connection under the bottom components

To be on the safe side I always double check the functionality of the light one more time before I close it. If all is well,

Close the case
Enjoy the light this evening

Step 4: Bonus Tip, Use Real Tiki Torch Holders

For an even more authentic look place these in actual Tiki torch stands. Because these lights are so realistic we replaced all of our liquid fueled torches with them. Using the original Tiki torch stands only presented one little issue. The lack of any support for the bottom of the light tube would cause them to tip at an angle in the stand. So, I made the gray disk you see in the pics on my 3D printer. Problem solved!!

Step 5: Extra Troubleshooting

Only a few things usually go wrong with any solar lighting of this type. I keep a large box full of old discarded solar lights as their components can be used to repair other lights still in service.

Battery: Check the battery first

A lot of the time, simply replacing the battery with a new one takes care of the issue. Test the battery on a volt meter - if it is charged, that is NOT your problem, and neither is the solar panel, as that keeps the battery charged.

Solar Panel: If the battery is not charged, is it the battery or the solar panel?

Locating the positive and negative leads from the solar panel is usually not an issue. Using a voltmeter, check to see if there is any output from the panel. The voltage should fluctuate depending on the amount of light hitting the panel. So if the solar panel puts out voltage, replace the dead battery. If there is no output from the solar panel, it needs to be replaced (after checking all connections first, of course)

On / Off Switch: If there is an On/Off switch, those are commonly an issue. The "On/Off" switch is only there for storage purposes. Turning them Off before storage prevents draining the battery too low.

Our lights remain outdoors all year, so I will bypass any "On/Off" switch that gives me trouble. Remove the wires from the button and connect them together. The lights are now permanently "On." Remember, though, that doing this does not affect the On/Off (day/night) function. A photocell controls that.

Photocell: built-in to the solar panel or a stand-alone component of the light

To locate the photocell, look for a small round shape on the top of the solar panel or in the light case itself. A bad stand-alone (in the case) photocell can be replaced. A bad photocell in the solar panel requires replacing the panel.

Wiring: check the wiring in general

It is also common to have a wire come loose. Look at each connection, and repair any not looking 100% healthy.

Circuit Boards: even the cheapest of solar lights will likely contain a small circuit board

Has that board been compromised by moisture or pests? Hopefully, a good cleaning will help, or perhaps a bad capacitor or resistor can be replaced. Otherwise, it goes in the old discarded box.