Baby refuses to sleep in cot

We have never ever let our baby cosleep with us ever. She has also slept through the night since about 2 months old. Shes 9 months old and now will not stay asleep in her cot for more than half an hour. She will wake up and cry, weve tried letting her cry but she doesnt stop, then i pick her up and shes asleep instantly. Then i lay her back down in her cot and she wakes, but if i lay her in our bed she stays asleep, so i move her back and she wakes again. Its an endless cycle and not quite sure what to do about it