SQL Doesn't start and Event ID = 17204

After hardening a server, the service didn't start anymore and I found the following error:

Event ID = 17204

FCB::Open failed: Could not open file C:\Program Files\Microsoft SQL Server\MSSQL10_50.MSSQLSERVER\MSSQL\DATA\DemoData.ldf for file number 2. OS error: 5(failed to retrieve text for this error. Reason: 15105).

Details:

The File C:\Program Files\Microsoft SQL Server\MSSQL10_50.MSSQLSERVER\MSSQL\

DATA\DemoData.ldf  in the message is not accessible to SQL Server for read and/or write 

operations during startup or database recovery. SQL Server might not be able to find the file, 

the file may be locked by another application, or SQL Server may not have permissions to 

access the file. 

Solution: 

• Check that the file listed above is exist in the specified location.
• Check the read write attribute for the file.
• Check the SQL Server startup account has read and write permission to the folder and file.
• Check that the file is not opened by another process.
• Check that the file is not encrypted.
• Provide FULL CONTROL (not just modify) to the service logon account (in my scenario was Network Service).