Why does my Krups Cafepresso Plus machine stop producing expresso coffee?

Hi
I've a Krups Cafepresso Plus machine which has not been in use for several years. I added some vinegar and water to run it through and check if it still works.
The water passed through with the filter coffee option so this part is working.
But for the expresso (steam) coffee part, it spurt some water into the cup and stopped. Now it doesn't even steam or have any water going through.
There is no leak at the bottom of the machine. How am I able to get water through the expresso part if there is a clot?
Thanks
Peter