Rigify IK-FK slider broken after appending

I’ve appended my rig from another file and so far everything seemed to work just fine. The rig main properties panel is visible and works. Expept for the IK-FK slider. Changing it has no effect.
I have tried rerunning the pythonscript, but that didn’t fix it.
I would really like to not have to redo the whole riggify thing since ive allready done a ton of animation, and also plan to append more rigs in the future. Is there a way I can just find the broken connection and fix it?

For now I’ve found a workaround, which is posing the FK bones and snapping the IK bones afterwards, and vice versa. But thats obviously not perfect.