Hi Tapas,
Your login supports admin users or not, it is probably however that its made to login with application users (users which you create on Users and have roles for your applications). In other words, your application user provider in that case is Users, which you can see by checking the module details.
You can however change that to login infrastructure users, i.e. users with access to Service Center and Service Studio. For that, you just need to change the property User Provider module property to Service Center.
Hope it helps.
Kind Regards,
João