Be sure that all of your equipment is sterilized by using boiling water or sterilizing your equipment in the dishwasher. This helps prevent bad bacteria from forming on your yogurt.
In the bowl of your Instant Pot, combine the coconut milk and agar flakes and bring the mixture to a boil. (I press the Sauté button to do this.) Use a whisk to stir, helping the agar flakes to dissolve as the coconut milk boils. Once the milk has reached a rolling boil (or has reached 180ºF on your thermometer), turn off the Instant Pot and stir well, making sure all of the agar flakes have dissolved. Stir in the maple syrup, then let the mixture cool to 110-115ºF for proper fermentation, which feels warm to the touch without feeling like the temperature will hurt your finger. You can speed the process by placing the instant pot bowl in an ice water bath, but be sure that it doesn't cool too much. Use a thermometer or a clean finger to judge when the coconut milk has reached 110-115ºF.
Once the coconut milk has cooled to the proper temperature, add in the probiotic powder and stir well. Press the "Yogurt" button on the Instant Pot, and then use the arrows to set the amount of time you'd like the yogurt to ferment. I recommend letting it ferment for 18 to 24 hours for tartness, but you can do it in as little as 8 to 10 hours if you don't want a tart yogurt. Place the lid on the Instant Pot to help keep the yogurt clean and at the proper temperature. (The pot will not be pressurized, so don't worry about the vent position.)
Once the yogurt has fermented, be sure to taste it to make sure it has become tart enough to your liking. The texture will still be watery and separated, with a possible cream-colored film on top, which is normal. (If there is a pink or gray colored film on top, that's a sign that the yogurt has gone bad and you should discard it in that case. When yogurt doesn't ferment correctly, it smells VERY bad and is nearly impossible to miss. Trust me on that one.) Pour the yogurt into a clean jar with a lid, and store it in the fridge to set. The yogurt will thicken when chilled.
The coconut milk yogurt may separate a bit when stored in the fridge, so stir it well before serving. It can keep well in the fridge for at least a week, if not longer.
If you don't have an Instant Pot, make this yogurt on the stove top. Simply bring the milk to a rolling boil on the stove top and dissolve the agar flakes by stirring with a whisk. Pour the mixture into a very clean jar, add the maple syrup, and allow to to cool to 110-115ºF. Stir in the probiotic powder, seal the jar with a lid, then wrap the jar in a towel to keep it insulated. Store it in a warm place, such as in your oven with just the light on. (Some ovens have an option to stay warm at 100º, if you have that.) You can also use a yogurt maker, a dehydrator, or a heating pad set to very low to keep your yogurt warm. Be sure the temperature doesn't exceed 115ºF or you'll risk killing the good bacteria. Just like the recipe above, you'll want to ferment the yogurt for 18-24 hours for the best tart flavor.