When using both Numismatic Overhaul and Bigger Stacks, the game crashes before it finishes launching. I'm guessing this is a conflict between the embedded stacc-api lib and Bigger Stacks, as they are both trying to modify the maximum stack size. When either of the 2 mods are disabled, the game launches fine.

[pool-4-thread-1/WARN]: @ModifyConstant conflict. Skipping biggerstacks.mixins.json:vanilla.stacksize.ServerGamePacketListenerImplMixin from mod biggerstacks->@ModifyConstant::increaseStackLimit(I)I with priority 1000, already redirected by stacc.mixins.json:CreativeDesyncFixin from mod stacc->@ModifyConstant::max(I)I with priority 1000

Is this regarding Numismatic Overhaul Reforged? If that's the case, we do not maintain it. If you are using this via something like Sinytra Connector, then that would probably be something they could look into (maybe a compat layer in Connector Extras?). As of 1.21.x we don't use Stacc anymore, as vanilla allows stack sizes up to 99.