It's set up to use potions to cure yourself if you click cure - specifically the Robust x Remedy ones. If you don't have them it will fail.
I have not touched the click cure functionality in a long, long time. As I recall I had to change it way back when because DBG messed up the /cureplayer command to not use potions properly so it stopped allowing you to pot cure yourself - which is the most critical need as it satisfies all classes. I'd have to test to see if it's feasible to fix or not, as I honestly don't recall if they ever fixed the higher-end potion cure functionality.
If you want to fix it for yourself in the meantime, you can edit the _Fetish_clickcures.xml and search for "CastMe" and replace the use_itemvdl statement with cureplayer g0 <det type>.