Make sure the capitalization is correct, in both the username and password. If it continues to not work, click "forgot password" and it'll help you regain access.

(The fd-user suffixes only applies if you have a Gamepedia account with the exact same username. If that's not the case, ignore that notice).

If you don't have a registered email address on that account, try contacting staff for further help.

Alright, I will try that! Thank you c=

Minor correction to what GarfieldTC said. The suffix is added if a Fandom and a Gamepedia account have the same name. It does not matter whether or not the accounts are owned by the same user. If a Fandom account was forced to change, "-fduser" was added. If a Gamepedia account was forced to change, "-gpuser" was added. Users who had their accounts renamed like this get 1 additional account rename. If you want, you can read a details in this staff blog.

Thank you for linking the blog, that was an interesting and informative read! Resetting my password has fixed the issue so thank you for the answers!