Just thought I'd share this as others might experience this in the future while accessing your Good to Go account online.

Yesterday I decided to check my account balance since I've used 520 a few times lately since tolling started.
I was unable to login using my username and pin. My account was established when I got my passes for free when the Tacoma Narrows tolling came on line.

I ended up talking to a customer service rep. He said that since my account was one of the first established, it got deleted when the state acquired new servers. I asked why they simply wouldn't have migrated my account to the new system? He said he didn't know or have an answer for that.

So if you have an older account and aren't able to login, you'll need to re-establish your account with a new username and pin number.
Your available balance will still be there once you re-establish your account.