protected internal method telling can not change access modifiers when overriding in a different assembly

Question

I have two projects in one solution and I added a dependency of assembly A in the assembly B
So here I have the asembly A where I have the folloing class

public class Person {
    protected virtual void CalculatePay() {
        Console.WriteLine("CalculatePay in Person class.");
    }

    protected internal virtual void test11() {
        Console.WriteLine("test11 in Person class.");
    }
}

then I have the assembly B where I have the following class

class uno : Person {

    protected override void CalculatePay() {
        Console.WriteLine("CalculatePay in uno class.");
    }

    protected internal override void test11() {   //CS0507
        Console.WriteLine("test11 in uno class.");
    }

}

So I am able to override the protected method CalculatePay() just fine but when I try to override the protected internal method test11() I get the exception saying I can not change the access modifier of an overridden method but I am clearly not channging it.
The error goes away if I change the modifier of test11() from protected internal to protected in the class uno which is weird to me.
This happens only when I override in a different assembly. It does not happen when I override in the same assembly.

I think I am missing something here. Can you please tell me exactly why this happnes?