event %s does not exist, or was not safe for net

The problem

When triggering an event between client and server you get "event X does not exist, or was not safe for net" and the handler doesn't run.

The cause

The receiving side didn't register the event as a net event with RegisterNetEvent (it only used AddEventHandler), or the event name doesn't match exactly between the trigger and the listener.

The solution

Register the event as a net event on the side that receives it:

-- RECEIVING side (server.lua or client.lua)
RegisterNetEvent('mi_recurso:darDinero')
AddEventHandler('mi_recurso:darDinero', function(cantidad)
    local src = source -- on the server, who triggered it
    -- logic
end)

-- Modern short form (registers and handles in one):
RegisterNetEvent('mi_recurso:darDinero', function(cantidad)
    local src = source
    -- logic
end)

Step by step

1. 1.Use `RegisterNetEvent` on the listening side, not just `AddEventHandler`.
2. 2.The event name must be IDENTICAL in the trigger and in the registration (watch out for capitalization and colons).
3. 3.Check that the resource registering the event is started (`ensure`).
4. 4.Never trust client data on the server: always validate with `source`.