There's something wrong with the channel system in Izlude & Prontera Field 8 "South Prontera Field". New characters get forcefully logged off once reaching Prontera on the newbie channel, and they can't change to regular channel either. The only way to go to Prontera as a new player is to take Kafra warp.
A lot of people don't want to bother doing the questline, so they just get frustrated and quit. You better fix this.