Blackboard have released a fix for the issue affecting people joining sessions using Collaborate with the Original experience.
If you downloaded the Collaborate Launcher between 23 September – 8 October 2016, and you’ve had trouble joining sessions, you will need to download the launcher again – follow the link on that page to the test session, then follow the prompts to download the launcher.
Note If you followed the workaround instructions, installing the new version doesn’t change these settings back to using the Collaborate Launcher for .collab files. You will need to change them back.
Follow the steps of the workaround again, however this time in step 5 choose Blackboard Collaborate Launcher.