Error message codes are network connectivity errors - in other words, you may not be connecting to the internet.
Try an update or log in to confirm the problem still persists. Then try and browse to www.google.com with Safari - if this fails, it is likely the whole tablet has a network connectivity problem.
If www.google.com works, see if you can browse to www.stellarlibrary.com and then click on the login link. If the Login page appears then the Stellar Library App should be able to talk to the servers.