I am having the exact same issue someone else reported back in 2015.
http://forum.newsbin.com/viewtopic.php?f=43&t=38584
I just signed up with newshosting today and I kept getting a 502 error first I thought I put my username and password wrong but I kept trying nothing helped tried other readers worked no problem. The only way I can an get to work is completely uninstall newsbin and start over. Even when I try and use a old nbi file the problem comes back and I have to uninstall again. Once it is working I still get a a few connections during a download that will give a 502 newsbin does not like something with newshosting