Some users may get returned to the login screen when logging into Blackbaud.com.  This issue may occur when confirming an invitation email for the Raiser's Edge NXT.  
Follow these steps to resolve the issue:
  1. How do I clear my browser cache, cookies, and temporary Internet files for Blackbaud.com
  2. Attempt to log into Blackbaud.com again
If you still experience the issue, chat with Support and reference this Knowledgebase article.