You mean, you are getting an error trying to register your account as a signal to MQL5?
Have you put correctly: account number, investor password and broker server (that's important too)?
What exactly do you try to do over your iPhone?
You have to put:
Login: account number
Password: investor password
Broker: type in your broker's server
So, something must be wrong, try to reset your investor password and try again.
If it says authorization failed, the MQL5 system cannot find your account data.