The kiosks will not let you print out a boarding pass within 30 minutes of departure time. AS contract of carriage says you have to be checked in and available for boarding 30 minutes prior to scheduled departure. So yes, they are within their rights to refuse to reprint your boarding pass if you arrived at the airport within that timeframe.

I also had WN refuse to print a boarding pass within 30 min of departure one time. They gave away our confirmed seats and then at the last minute, we got on from the standby list.