battery usage by app not available

So recently I brought an iphone 12 pro max and its been 20 days since I bought it but yesterday night at 8 oclock I charged it to 80% , then used for some time and then went to sleep at 11:30 and then I woke up at 4 oclock to my surprise my iphone wasn’t switching on so hold the power key ,I was Shocked to see that my battery was completely drained , I put the iphone on charge and then checked the battery usage , but from 12 am to 4am it said battery usage by app is not available(you can check the battery pic below),I never let my charging percentage reach 0% , Till now I have always kept it between 30% to 80%