I cannot open a trade; the New Order button is not active.

The MT4 platforms provide two types of passwords to access the account with. The Master Password is the trading password. This is the password you should use to login and trade with. The Investor Password is a read-only password. If you use this to login you will have access to the account, but you will not have any trading functions. By using the Investor Password, you will not be able to open/close trades or modify orders.