Not being able to enter Party instance
One time, I thought I had the same issue as you and that I could not join others’ Fractals as when I went up to the Mistlock portal, a text box opened up and asked me to create my own Mistlock instance as opposed to joining my party’s instance.
It turned out that this was actually the text box asking me to join my party for some reason, and that if I clicked to create my own, it would put me in with my other party members’ instance.
Perhaps that is the same issue happening with you?
I tried that as well, it puts me into my own instance of that dungeon. i tried the box, walking up to the portal to make the other box appear nothing is working.
This occurred during one of the patches but here’s what I found is the way it behaves
1. If you wp to any wp that will induce a pop up window on the lower left hand corner, it will default to your max personal reward. Just click enter fractal and you should be in the same instance.
2. If a window pops up at the fractal entrance and you have a higher fractal level than the instance, you will need to select the level of the instance(I.E., your reward is 50 and the party instance is 20, select 20), otherwise if you’re lower just click enter. You should be in the same fractal instance.