Register a DB Context with Simple Injector and .Net Core

You need to tell SimpleInjector how to instantiate the UsersDbContext which seems to have a constructor with the parameter of type DbContextOptions.

Change how you register your DbContext by using an overload of Register method that take a delegate (factory) parameter like below:

container.Register<DbContext>(() => {
    var options = // Configure your DbContextOptions here
    return new UsersDbContext(options);
});