how do i log back to my old account?

[76561199143353835]

so i relog my steam account because there was some problem and then when i open quaver, my account have become a guest. when i click the login button, the game told me to enter a name and when i enter my old account name, the game said the name has already been taken.
sorry for my bad english and plz help

[ChiknLickn]

When you try to sign up for an account a name might have been taken so what i think is happening is you pressed sign up not login or sign in