Unable to activate plugins or find sites in admin panel

I'm not sure exactly when this happened, but I am no longer able to authenticate through the WPMU Dev Dashboard, see my sites listed on WPMU Dev, or activate plugins!

When I attempt to log in, I get the error: Your server had a problem connecting to WPMU DEV: "HTTP Error: 403 "Forbidden"". Please try again.

Thank you for your help!