Unable to verify this iPhone has a genuine Apple battery.

I charged my iPhone 11 Pro to 100% which I unplugged and went to bed. Woke up and checked it (I originally wanted to check the other phone I was charging so I checked it too) and twas still at 100%.

But by the time I woke up this early morning and wanted to use it and I saw it was now at 1%; which surprised me. So, I tried plugging in my charger to it but twas not charging (just stuck at that 1%).

Decided to check the "battery" in settings and the battery (capacity which was at 81% previously) was now at 0%. And I saw a message that says;

"Unable to verify this iPhone has a genuine Apple battery. Details from this battery may not be accurate."

Pls, what exactly is wrong?