With any tinder, you have to be totally aware of the relative humidity in the environment. Dry that tinder fungus in the sunlight, or in your oven on low heat( 200 degrees) for an hour. Put it spread out on a cookie sheet, then store it in a ziplock bag to keep moisture from the air away from it. Those thick patches are difficult to light, even when you have charred them because they too take on moisture from the air, and hold it. The thin T-shirt( 100% cotton) work so well BECAUSE THEY ARE TOO THIN TO HOLD MUCH IF ANY MOISTURE!
You can light milk weed, but again, it needs to be charred, and kept dry. Starting a fire with flint and steel and charred anything is hard work when its humid over overcast out. When the sun is out to dry up everything- even hemp rope that has been sweated on by your hands when you pull the strands apart will Light with a bit of effort, after drying in the sun on a stump or rock, or log. I Have actually had better success getting my char cloth to light with a pile of embers I generated using a Bow and drill fire starting tool, on wet days.
If there is a lesson to be learned its to use the thinnest charred material you can have, or make, and to dry any kind of natural tinder you pick up in the woods. I collect strips of bark off of White bark Birch trees, because the bark is thin, and contains natural oils that burn hot very quickly. But you have to live in northern latitudes, or have access to ornamental birch trees on private properties to get the stuff. Same for the tinder fungus, as its most often found growing in a bruised area of a birch tree.
Assume that anything that is picked up off the ground is too moist to light.
Tinder for building fires should be taken from dead limbs of trees and bushes, where air dries the wood, and the bark keeps moisture from penetrating into the core. If a twig bends, rather than snaps, leave it. Its too moist, and will only burn with lots of steam and smoke, if you can keep it lit. If you do dry that tinder fungus, you will easily find out how brittle the stuff becomes when you break off a piece to use.