Please urgent! Help with humidity in terrarium

[Bogertophis]

I think it's just fine to use your dehumidifier in the room.

About leaving the coconut fiber in the sun, that's fine too- I'm assuming you're talking about just the fiber, not the tank with the snake & all, as sun can easily overheat any enclosure & kill your snake. (I'm just making sure we're on the same page. )

Some people also bake substrate or small branches & wood furnishings in a "low & slow" oven too -but do be careful not to set anything on fire- you'd only use 150* F. for about 45 minutes, & well-supervised; some also do this as needed to kill harmless insects (or potential pathogens) that sometimes 'invade' products.

It's possible that the coco. fiber in the cage got too damp-? If it's still clean, you could scoop some out (to dry it out), & replace it with the dryer coco. fiber. It's hard to say what's really needed without an accurate humidity gauge- the pandemic has messed up plenty of commercial shipments & other business dealings.

We typically see glass tanks with screen tops- in looking at your photos, it's hard to see where the ventilation is? Maybe that's why you're getting so much condensation?

One more suggestion: You've done an attractive set-up, but I only see one hide: your snake needs at least 2, one on the warmer side & one on the cooler side, so he can "thermoregulate" (ie. choose the correct temperatures for his needs at all times). All snakes need options for hides: if only given one hide, they'll choose to hide in it, instead of choosing the correct temperature, so if (for example) they've just eaten, they might be too cool to digest well if the hide is on the cool side; it's no better if there's only one hide on the warm side either- they shouldn't stay the same warmer temperature all the time. A snake's metabolism depends entirely on their temperatures & their needs change frequently; in shed, they usually prefer to be cool.