Help!!! 9 month old sleeps like an 8 week old

My daughter is 9.5 months. She has been a horrible sleeper since day 1. I honestly feel like I haven’t slept since I was 5 months pregnant and survive only with the help of coffee. We started a gentle approach to sleep training about 2 weeks ago. She is now going down great every night, no crying or protesting..... except she only sleeps 2-3 hours and then is up and full of it. It sometimes takes me or my husband a couple hours to get her back down. And even after all that she only sleeps for another 2-3 hours and then we start the process again. All the websites only refer to what to do to get the baby down in the evening. They don’t talk a lot about what to do if the baby doesn’t stay asleep. Anyone been through this???