IPhone activation lock
My iPhone has an activation lock when I try to open it it says ID incorrect but it is the same ID I use even when I check it online I was able to log in to my account and I checked the device it was the same device with the same serial number. I'm able to log into my account online but not able to log into my phone when I try to activate my lock please can you help me understand what's wrong with my phone because I've been using this Apple ID for long
iPhone 5s, iOS 12