CactiGuide.com

Hello all. Really hoping someone can help. I got a lovely Euphorbia Eritea for Christmas last year and in the last few months it is looking worse for wear. It is living in a bay window with net curtains and there are other plants there that are thriving, however the cactus seems to have shrivelled and is dry and crusty to the touch. I have been watering it once a month in the winter months and once a fortnight in the summer. It started with a couple of the "arms" turning a dark colour and shrivelling but now it's the whole plant. I can't attach a photo for now as I'm on my phone and the file is too large but if you feel it's necessary I will reduce the file size and try later. Any help in the mean time much appreciated. Really hope I can revive this beauty. Thank you.

It sounds like either you haven't been watering it anything like enough, or the roots have died (which is quite often from over watering), so the plant has not been able to take up any water. Check the pot has a drainage hole and the soil is free draining and doesn't retain too much water.
You may be able to rescue the plant by keeping the compost just about moist, or else by taking cuttings of healthy looking branches and rooting them.