SqlExcepction 0x80131904 in ASP.net. Website can't connect to SQL Server, error 40 -

so i'm getting error company's asp.net website (built on old dotnetnuke framework) today says:

a network-related or instance-specific error occurred while establishing connection sql server. server not found or not accessible. verify instance name correct , sql server configured allow remote connections. (provider: named pipes provider, error: 40 - not open connection sql server)

and lists stack:

[sqlexception (0x80131904): network-related or instance-specific error occurred while establishing connection sql server. server not found or not accessible. verify instance name correct , sql server configured allow remote connections. (provider: named pipes provider, error: 40 - not open connection sql server)] system.data.providerbase.dbconnectionpool.getconnection(dbconnection owningobject) +428 system.data.providerbase.dbconnectionfactory.getconnection(dbconnection owningconnection) +65 system.data.providerbase.dbconnectionclosed.openconnection(dbconnection outerconnection, dbconnectionfactory connectionfactory) +117 system.data.sqlclient.sqlconnection.open() +122 microsoft.applicationblocks.data.sqlhelperparametercache.discoverspparameterset(sqlconnection connection, string spname, boolean includereturnvalueparameter, object[] parametervalues) +233 microsoft.applicationblocks.data.sqlhelperparametercache.getspparametersetinternal(sqlconnection connection, string spname, boolean includereturnvalueparameter) +343 microsoft.applicationblocks.data.sqlhelperparametercache.getspparameterset(string connectionstring, string spname, boolean includereturnvalueparameter) +175 microsoft.applicationblocks.data.sqlhelperparametercache.getspparameterset(string connectionstring, string spname) +45 microsoft.applicationblocks.data.sqlhelper.executereader(string connectionstring, string spname, object[] parametervalues) +207 dotnetnuke.services.log.eventlog.dbloggingprovider.data.sqldataprovider.getlogtypeconfiginfo() +71 dotnetnuke.services.log.eventlog.dbloggingprovider.dbloggingprovider.getlogtypeconfiginfo() +101 dotnetnuke.services.log.eventlog.dbloggingprovider.dbloggingprovider.getlogtypeconfiginfobykey(string logtypekey, string logtypeportalid) +65 dotnetnuke.services.log.eventlog.dbloggingprovider.dbloggingprovider.addlog(loginfo objloginfo) +75 dotnetnuke.services.log.eventlog.logcontroller.addlog(loginfo objloginfo) +175 

i had take site down recently, did moving files section of hard drive. when moved them back, got this. it's connecting separate server have, there's block somewhere in connection. both machines able ping each other, i'm guessing it's on server level? stack vague me, don't have first clue of error. thoughts?

i start doing following.

go http://servername/install/install.aspx

see if dnn gives additional details on connection error.

check web.config connection strings. did setup iis use dynamic account owner of application pool? login information in web.config connection strings still work?