Bring SQL Server database online

I think you're going to need to login with the SA account, or some other account with sysadmin privileges, and then run your code to put it back online. While you're in there, add sysadmin to your account, too. If you don't own the database, you may need to talk to someone else to get the SA password, or ask them to do it for you. Unless you don't have the SA password or it's been dumbed down for security reasons.