Hello there Kjelle.
On way to handle your situation would be to send the player a forum pm to let them know that you've been waiting for a while for them to respond.
The second option would be to contact an admin and let them know. The admin will continue the auction for you, calling "Going once" & "Twice" etc. This is usually done by an admin if the player hasn't made the call after 48 hours.
Since you've been waiting for 5 days I recommend asking an admin to look at the auction and to continue it for you since the player seems to not be active in the auction.
Feel free to reply with any questions or concerns you might have. I hope this helps