P99 requires the
Titanium client (but that doesn't look like the Titanium login screen to me); see
https://wiki.project1999.com/Getting_Started for further info.
P.S. You said it was working before ... did you possibly run the live patch by accident? If so you will need to reinstall.
P.P.S. If that's just a weird login graphic, but you
do have Titanium, then you are probably running into the (common) networking issue here. Using a VPN is a known workaround, but you can also read heavily in the Technical Forum for solutions for your specific setup (if you don't want to use a VPN you're going to have chase down whether the problem is your computer, modem, router, etc.).