You state in your question that your SP2010 Web Application was using Classic mode and you migrated it to Claims-based authentication using Windows NTLM. At the same time, you also enabled Forms Based Authentication.

The article you referenced in your question is for a new web application using Claims with both Windows and FBA authentication. The web application in this article never was configured to use classic mode.

This is not your situation as you are migrating from an existing web application. The article you need to follow is here Part 2 with Part 1 located here as a reference. The MigrateUsers method on the SPWebApplication object is needed to convert the users to Claims mode. Powershell commands in the article explain how this is done.

You state in your question that your SP2010 Web Application was using Classic mode and you migrated it to Claims-based authentication using Windows NTLM. At the same time, you also enabled Forms Based Authentication.

The article you referenced in your question is for a new web application using Claims with both Windows and FBA authentication. The web application in this article never was configured to use classic mode.

This is not your situation as you are migrating from an existing web application where classic authentication is already enabled. The article you need to follow is here Part 2 with Part 1 located here as a reference. The MigrateUsers method on the SPWebApplication object is needed to convert the users to Claims mode. Powershell commands in the article explain how this is done.

You state in your question that your SP2010 Web Application was using Classic mode and you migrated it to Claims-based authentication using Windows NTLM. At the same time, you also enabled Forms Based Authentication.

The article you referenced in your question is for a new web application using Claims with both Windows and FBA authentication. The web application in this article never was configured to use classic mode.

This is not your situation as you are migrating from an existing web application. The article you need to follow is here Part 2 with Part 1 located here as a reference.

You state in your question that your SP2010 Web Application was using Classic mode and you migrated it to Claims-based authentication using Windows NTLM. At the same time, you also enabled Forms Based Authentication.

The article you referenced in your question is for a new web application using Claims with both Windows and FBA authentication. The web application in this article never was configured to use classic mode.

This is not your situation as you are migrating from an existing web application. The article you need to follow is here Part 2 with Part 1 located here as a reference. The MigrateUsers method on the SPWebApplication object is needed to convert the users to Claims mode. Powershell commands in the article explain how this is done.