I had the exact same problem playing with my friends online. They could see my character while I couldn't, yet I could do nothing. When the party leader tried to go far away to teleport me to him, it didn't work, my character was stuck with "Teleporting" message, and disappeared after a while. When he tried to rest, it teleported me on camp, but I was still unable to do anything, and when I jumped and disappeared on the ground, I teleported back to where I was before.
I had the exact same problem playing with my friends online. They could see my character while I couldn't, yet I could do nothing. When the party leader tried to go far away to teleport me to him, it didn't work, my character was stuck with "Teleporting" message, and disappeared after a while. When he tried to rest, it teleported me on camp, but I was still unable to do anything, and when I jumped and disappeared on the ground, I teleported back to where I was before.