With no info, it's hard to say. Was your 9mo sleeping through the night before? Did she went through a change recently (change in routine, daycare, etc.)? How is her nap schedule during the day? Does she have too little sleep during the day? Too much? Is she teething? Does she usually soothe herself back to sleep? Does she absolutely need to be picked up or are you able to guide her back to sleep with words? How often does she wake up? There could be so many reasons for her to wake up like this...
Around this age it can be object permanence issue, a habit issue, and sometimes a combo plus reverse cycling. Some bloggers I’ve gotten good info from is the peaceful sleeper and taking cara babies. For us, we limit our baby’s day time sleep or else if she sleeps over 3 hours total, she’s very restless at night and will do an early wake. Sometimes it’s about finding out what baby’s threshold is as far as total sleep time or bedtimes and awake times. I know that’s so controversial to wake a sleeping baby but I’d rather her have restful deep sleep at night when it’s more healing. Nap time is not supposed to be deep sleep time.
I asked our pediatrician about sleep training at our 9 month well visit, and she said at this age it is still normal for infants to wake up once or twice over night. My little guy is struggling with solids and the doctor thinks he is waking because he is hungry and strongly recommended we do not sleep train at this time.
It might be worth checking in with your pediatrician.
Taking Cara babies is an awesome resource I used. They have a website and free blog that has scheduled guidelines you can use if you don’t want to pay for the classes. All three of my kids slept through the night from 4 months on when I implemented the free material she provides. Making sure they ate enough during the day and keeping their naps in check was really the big factor for me and my babies. Like noted above, without a lot of background info it’s hard to say what might be causing it but this is what worked for me so I hope it helps!
Re: 9 month baby doesn’t sleep through the night HELP
It might be worth checking in with your pediatrician.