SQL Server queries fails with error

“Operating system error 1909(The referenced account is currently locked out and may not be logged on to.).”

when SQL Server or agent startup account is locked and if you try to access the network path etc .. using SQL command operating system will return this error.

Ex:”RESTORE DATABASE test FROM  DISK = N”\\ServerName\Backup\test.bak”

Above restore command would fail with error
“Operating system error 1909(The referenced account is currently locked out and may not be logged on to.).”

Reason

SQL Server startup account (or) SQL Server agent startup account is locked.

Resolution

Unlock the startup account