Unable to Login in MT-4

@ Hariyanto:

It is likely that the server on your account is inactive or n/a (not available). For demo accounts, the server can sometimes be inactive. You can check this by left-clicking the bottom right of the platform, which will display a list of active servers with their respective ping sizes:

Then check your account by going to File - Login to Trade Account, adjust or select a server that is active and has the smallest ping number:

After that, left-click the bottom right of the platform again, and Rescan servers.
If it still says invalid account, try restarting MT4 by exiting and logging back in. If it still fails, you must create a new demo account, note the server and adjust it to the active server.