Same happened with me also as recently I was busy with some of my assignment work of University and had installed Google Classroom in my phone to do all assignments. I’ve been trying to use the Google Classroom app on my phone but with no luck. When I try to add my school Google account on the Google Classroom app, it always prompt to enter the current pin.
Google is one of the top app and web content developer. Android is one of the most used Operating System for mobile devices[famous also]. There are various possibilities like when we met some serious issues in our device but after getting the solution of those issues, they seem smaller than what we expected.
After some Google and many other help sources I came to know that this is just a small problem and particularly You just need to put your phone’s Pattern Lock there to enable the further process of adding an account.