This is a sight you haven’t seen in Budapest-Keleti since September: A Euronight train waiting for passengers to board.
Indeed, my visit there coincided with a brief period when international rail services were running as normal despite the migrant/refugee crisis.
There continue to be some disruptions because of temporary border controls relating to the flow of migrants; do check with your operator — and alternatively, see this list of service disruptions from Eurail — if you had planned to use rail services in this region.
If you are in Budapest and need help, the international ticket office on the ground floor (near the taxi stand entrance) is the better option. The domestic ticket office on the lower floor doesn’t always have staff on duty who are able to speak English.
Although the Eurail link above refers to a business lounge at Budapest-Keleti doubling as an aid office for Eurail ticket/pass-holders, that part of the station was under renovation, with the lounge out of service as of September. Perhaps the situation has changed since then but do be aware of this possibility anyway.