Central Administration shows error 26 - A network-related or instance-specific error occurred while establishing a connection to SQL Server

Question

i Follow this Article to Config FBA , BUT after Step 3 , My Central Administration shows an Error :

A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 26 – Error Locating Server/Instance Specified)

Correlation ID: 89651359-9c57-4241-8254-eb3be052c4f0

Now , i cannot access to my Central Admin Setting (All links in page), but my site Collections works well.... i Rollback all setting but no Effect !!!!! i execute iisreset but nothing !!!! what should i do? please help me.. Thanks in Advanced

Answer 1

Make sure you're not switching Central Admin for use Forms authentication and using any of the FBA providers as default

Answer 2

i find the Answer (Follow this Thread)

it's for Web.Config file of Central Admin