New GroupCalendar 4.0, is not compatible with previous versions, but is a major upgrade, including sign up slots by ROLE ie tank etc, so that dps warriors and tanks are signing up for different slots.

Remember, to setup,

"use guild data channel"

"use server dates/times"

"minimum rank to show - veteran"

http://wow.curse.com/downloads/details/1958/

again, as a last resort, u may use the website to sign up, but i stronly encourage people to take the time to figure out gc!