I get the same message using Chrome on a Macbook.
Access Denied
You don't have permission to access "http://sa.www4.irs.gov/irfof-wmsp/login" on this server.
Reference #18.a701e8ac.[phone number removed].77896a49.
TurboTax's messaging app seems to think there's a phone number in the IRS reference. If there is, it's not one that I recognize.
I'm inputting my address exactly as it appears on mail sent to me by the IRS so that can't be the problem. I thought it might be because I'm trying to access the application from outside the US but it doesn't work using a US IP address either.
Also, despite several unsuccessful tries, it does not appear to have locked me out.
I had no problem accessing it for the first and second payments, only the current one.
