Soul Offering not working and not editable

I'm a chronomancer, lvl 89 with 324 int and 151 spirit, trying to use a lvl 19 soul offering with a lvl 19 skeletal cleric.

The ability cannot be used in any way; it is placed in the skill list, but cannot be used or shown in the description when clicked.

I was able to use the ability a few hours earlier, but I cannot now for some unknown reason.

I have a video showcasing this bug: https://youtu.be/VRDPSZEsgcY