Moon, Silver and me Quest

In this quest you have to stand on a specific spot and summon a big monster and you have a bomb that you then need to explode.

For some reason the bomb just sits there next to the name of your quest on the monitor and you try to pick it up and does not work well, several tries. I also tried to put it into the Quickslot but that, even though I used it, worked as a bomb but did nothing to the mob who just killed me.

So I go all the way back and tried again, got the bomb to function but the big monster then still kills me with two or three hits.

Tried it again but was unsuccessful.

This is not a compulsory quest but gives good gloves which i need. But maybe it is bugged so I thought mentioning that could do not harm

Generally the way these quests work is you use the key item which places a debuff on the mob and then kill it normally.
What happens when you try to use the item? Nothing at all or is the cast being interrupted?