I am trying to add the vanilla bow in the Infuser but is not working.

Does any other tool work? E.g. a stone pick?

Yes, tools armor, and weapons work, even other moded items.
The same problem happens in the Easy Magic table.
I can't add the bow to it.
Is it because the bow has some used durability?

No, durability isn't an issue. Can you enable advanced tooltips (press F3+H) and send another screenshot fo the tooltip?

Here

Hmm, that's not it then. You happen to have any other mod that makes bows stackable? That usually messes up enchanting.

So besides that, it's probably a mod conflict. You'll have to make a test world and keep removing mods until you find the one responsible (remove half the mods, then the half from that and so on, always keep going with the half that has the issue). I know this is super tedious, but there doesn't really seem to be an obvious cause here.

Which one is it?

Yeah, I do have a stackable mod, I mainly use it for the boats and other bothersome non stackable items, but is an all-or-nothing case, since it does not have an item filter. it's the only one available for 1.18 at the moment.

Stackable Everything https://www.curseforge.com/minecraft/mc-mods/stackable-everything

I used to use Upsizer Mod [FORGE] https://www.curseforge.com/minecraft/mc-mods/upsizer-mod
But it got no 1.18 update

Stackable Everything isn't really an alternative, I'd very much recommend against using it. You're not the first person to report an issue with that mod. So that mod is at fault, therefore closing this issue.

Oh well, it's a shame Upsizer hasn't gotten an update, it seems to be quite alright for what it does.
I'll ask the creator of Upsizer if they'll let me update the mod, it's not much work and maybe they agree.