I'm just logging this here as an issue with a solution so that it may hopefully help out other people. We have Webwork 2.16 set up to authenticate via Blackboard. Homework links were working perfectly for most students but we had two or three who could authenticate fine from Blackboard to the homework but once they clicked on a problem it brought them to the Webwork login page. It turned out that these few students were accessing the homework via the auto-generated link on the Blackboard calendar. Once they clicked the direct link it worked fine. In the process of debugging this I also noticed the same issue would occur if the homework wasn't opened in a new window when the link was clicked in Blackboard. When creating the homework link we had to ensure that ‘Open in New Window’ is set to ‘Yes’ in Web Link Options.
TLDR: Tell students not to access Webwork homework sets via the Blackboard calendar. Make sure when you create a new homework link in Blackboard to ensure that ‘Open in New Window’ is set to ‘Yes’ in Web Link Options’
All the best