I have a Multi Tenant SharePoint 2013 environment configured for FBA in Windows Azure, with SharePoint 2013 and SQL Server 2014 on separate VMs. For every tenant, the SQL connection string dynamically gets the User DB name in the Custom Membership Provider. Everything was working fine and I was able to login with the Forms user. Due to some other issues, I had to delete and recreate the User Profile Service Application. After this, I found that my FBA login is no longer working. It is not authenticating the user. I have no clue, what permissions got changed because of the recreation of the User Profile Service, because of which I am facing this issue. Unfortunately, I have no Visual Studio in that environment and hence I can't even debug the custom membership provider to see, what is going wrong with its ValidateUser method. Can anyone please help?
It may sound weird. But I had to redeploy the Custom Membership Provider assembly into the GAC and reset IIS. I went into the ULS Logs and could see an error saying the credentials couldn't be validated with the user name and password or something like that. I had seen this exception before also. In fact, the same exception was getting logged into the Event Viewer as well. Hence I thought of redeploying the assembly and reset IIS and it fixed the issue. Hope it helps someone.