Dog will not stay asleep.

5 month old spaniel/lab/pointer mix.

We have had our dog for 2 and a bit months now. She's honestly amazing except she will not sleep through the night. She gets up at 3am and loudly whines and barks at the bottom of our stairs. We can't let her do this because we live in a terraced house.

She would fall asleep on the sofa at 10pm and we would leave her there or move her to her bed in the same room. She would then wake up 2-3 times a night and we would calmly put her back into her bed. Boring as possible, she then learned to self settle and we had a glorious few weeks where she would sleep from 10-5:30 consistently (we let her upstairs from 6am with an alarm).

However she has now learned that if she starts barking we have to respond. We can't leave her to get this out of her system because of the neighbours. We had started waking up at 3am again and will not resettle no matter what we do. When we try and leave the room it is immediately back to loud whining and barking.

I'm really at my wits end. My work is suffering from sleep deprivation and tonight was maybe the worst she's been (up at half 3 and she still hasn't slept at 20 past 5). I honestly don't have a clue what we do from here, we've tried several approaches and cannot get her to sleep through the night.