Firstly, make sure you using the correct login details. The login details for your Demo and Live accounts are different. Both would have been emailed to you separately, you may need to check your spam folder.
You also need to make sure you are selecting the correct server - Select Fair Forex-Demo if logging into a demo account and Fair Forex-Live if logging into your real account.
Make sure you are using the Master password NOT the investor password. The Investor password is read ONLY.
Also make sure you have downloaded the Fair Forex MT5/MT4 platform, and that you are not trying to log into a Fair Forex account from another brokers platform. If you are logging into the Mobile App, make sure its the correct one ie: MT5 or MT4.
These videos may also be helpful:
If you still need help, let us know and we can try resetting your password.