I have two answers for you;
First answer
When opening the page AddAccount you need to pass a AccountPasswordData object which does have a association to a App_User Object. Also the user must have access rights to read/write the attributes.
As far as I can deduct I assume you
Second answer
You mention registration of users “ For registration purpose in the registration page...”
Gives me the impression that you want the option for anonymous users to register them self and creating an account. See my answer on this post for the way how to do this: https://forum.mendix.com/link/questions/104377
He Gayatree,
Just a quick question to check if I understand: before opening the page, did you create the Persistent the app-user and the NP AccountPasswordData and stored the association between the two? If not, the page doesn’t have an object to edit …
One thing about the model: Mendix advises to use UpperCamelCase for your entity names:
”3.2 Domain Model
3.2.1 Entity Names
Most of the time, an entity reflects a real-world object that people can relate to. Therefore, the entity name should also reflect that object and identify its purpose. There are sometimes project-specific exceptions that lead to creating other types of entity, but that is up to you. The name of an entity is singular since an object is a single instance of the entity. A good example is using Customer and not Customers. Furthermore, we advise avoiding abbreviations, underscores, mathematical characters or any other special characters in the names of entities. Entity names also use UpperCamelCase, for example, HousekeepingRecord or LogEntry.”
You can find the best practices here: https://docs.mendix.com/howto/general/dev-best-practices