Email and Steam connected still can't log in

Hello dear staff,

I usually log in through Steam. But sometimes, although rarely, Steam goes down.
Well I still want to play during those times, so I installed the standalone client for that purpose.

My steam ID and Email are connected in my account settings. I get the error "The specified account does not exist" when I try to long into the standalone client.

Would love your help in the matter.

Will do