It looks extremely thirsty. If you haven't watered it recently, and the soil is dry, it could use a good drink. If it's dry - wet it throughly, through and through so that you're sure the soiul is moist throughout. Then increase the humidity around it. It should recover although you're going to lose some leaves.

If it's already wet - you'll need to remove it from the pot and check the roots to make sure they haven't rotted away. If they have then you'll need to clip some of it and propagate the clippings in water, or sphagnum or some other such medium. The main plant you'll need to trim the dead roots, and repot in a chunky soil mix. Water it and again increase the humidity and then let it sit.

Hopefully others will chime in and add their suggestions too.

Best of luck to you - but right now, if I were you, I'd still start taking cuttings and propagating.

Ha ha! I was just wondering if it was over watered. Mine is kept very dry and is huge and ancient. And I don’t think above the radiator is good for it, Nikita. Mine’s in an unheated porch. (Guessing you’re in the U.K. So am I.)

I tried not to overwater it so maybe I didn't water enough. I started sparying the leaves as well. Might be a good idea to move it away from radiator

spraying is thought to be useless by most of us ...

besides the radiator... im wondering what is behind curtain number one .. and if you may have scorched it a bit.. when it moved from its old house to yours.. if it is in direct sun???

i always like the propagation suggestion when i see very old plants in tiny containers ... check out some of these.. and make some young vibrant plants ...

https://duckduckgo.com/?q=Hoya+Carnosa+propagation&t=ffcm&iax=videos&ia=videos

and per above.. i wonder how long its been in that pot ... media is a water management system ... and it can and does break down over the years .... and that might be part of your problem with watering it properly ...

but that might be hard to do with a long viney plant ... so i would probably give it one heck of a pruning before i tried that with the base plant .. and the cuttings would be what i used to propagate ...

and most likely.. after i had a couple pots of new plants ... i would just throw out the old plant ... why bother at that point ..and i would have couple new plants to inflict on soon to be ex-friends.. lol... or maybe new friends..

ken

I would check the root health- might have been over watered then under watered at some point.

If you find that the mix is not holding moisture evenly or repelling it a bit, I would soak the whole plant under water. One this I will tell you is that a plant that size in a pot that size will dry out way to fast because the roots will take over the entire soil mass and over crowd the pot leaving you many dry areas just watering over head my hand. IT needs a bigger pot as soon as possible and a mix that will be porous and yet hold moisture. I think you are going to find the roots very tight or compacted and may have to spread or separate them apart a bit..

Until I can repot mine, especially the carnosa known to grow tons of roots , I have to sink mine under water to make sure every root is watered by letting all the bubbles come to the top until it's done.