I working on a modpack and the items I saw as rewards is not fit to the modpack so I wanted to change it, but when I added the rewards.json these lines :

{
"content": "oxygen_core.currency.money",
"unitWorth": 100,
"weight": 100,
"amount": 50
}
I got a crash, all time, and I tried to edit many ways, but nothing worked

The following crash :
crash-2020-03-13_17.10.43-client.txt

That's not the right registry name for the item, that's why. If you use the mod CraftTweaker, you can get the right name by using "/ct hand"

Its okay, but how can I check the name of the currency when it's a digital thing, the player can't keep in it's hand.

Oh, you can currently only make bounties for items in hand or for killing mobs. If there's a way to add currency to a player with commands, then you'll be able to do that in the future because I'll be making a new bounty type then (running commands as rewards). But for now, you'd have to use an item. Perhaps you could have it so that on your server there's an item that you can exchange for currency? Then you could use that item instead.

Then this issue seems to closed for the next update.
Thanks for helping and I'll waiting then for that update.

Well, only for 1.12. I won't be updating 1.12 anymore, unless there are some important bug fixes. Sorry about that!