At a loss

My kids won’t sleep. I feel like I’m going insane. My almost 2 year old won’t nap all of a sudden and wakes at 3am every single night. My husband and I take turns going into her room to get her back to bed but she just screams. At a total loss. No clue what to do right now and I’m so exhausted. Also have a 4 month old with a double ear infection so she’s not sleeping. Send coffee. And advice, please!