Trade is disabled due to using the investor password, not choosing the correct suffix or trading is disabled by the broker.
You have added the slave (send to) account using your MT4/5 investor password. Trades cannot be opened/closed/modified when using the investor credentials. To resolve this error simply update the account with your full MT4/5 credentials. Go to accounts, press manage on the problematic account, visit login credentials and re-enter your new credentials.
A suffix is a prefix appended to a symbol, for example, ".stt". Brokers can add suffixes to symbols for many reasons. When they add a suffix to their forex symbols, they often disable the normal symbols resulting in error 133 when you try to trade them. To resolve this error, simply add the forex suffix to your account. Go to accounts, press manage on the problematic account, visit forex suffix, scroll the list and find the suffix (for example .stt), add that to the suffix input box and press update.
Trading not enabled by broker
If the issue is not password or suffix related, it is likely trading has not been enabled or has been disabled on the trading account. You need to contact your broker and ask them why you are getting the error.