Referred to MT4 only.
This usually happens if the trader sends a request to the server and is trying to send one more trading request while the first order is still in process. To resolve this problem, simply restart your MetaTrader4 terminal by closing it and launching again.
This can happen in cases where there have been multiple mouse clicks. Please restart the platform and this should solve the issue.
Please make sure that you are using the correct password on the platform and check the server that you trying to log into.
To change your MT4 password, please log into your MT4 Platform, click on "Tools", then "Options", Click on "Change" next to the password Tab. Please enter your current password and enter a new one, then click OK. You can also change the password of your MT4 account by logging in the Clients Portal and choosing change passwords from My Account
Please uninstall the platform, by going to "Start" on your PC, then "Computer", and go to "C: drive". Please select "Program Files", and delete the file "ArgusFXMetaTrader 4" to ensure a full uninstallation. Please then reinstall the platform.
To change Password on your Android/iPhone please click on the "Settings" tab, then click on "Accounts". On the bottom right corner you will see a Key icon, please click on it. You will then get a pop up window to change your password.