If you try to log in and you get an error message, there are several things to consider:
First, make sure you are on the connection page and not on the one to register:
If you are sure of your password, that the capslock key of your keyboard is not activated and that you didn’t switch the keyboard language, then the issue might come from your browser. Some browsers keep certain data in their cache memory, that can create errors in some cases: this data is stored in cookies files. In this case, you need to clear your cache and cookies (procedure changes from one browser to another) or try to log in using a different browser.
In case the error persists, you can always make a request to generate a new password: