If you've accessed Collaborate previously, when launching a Collaborate session you will be offered the opportunity to update the Collaborate Launcher, whilst optional it is recommended to do so.
The first time you attempt enter a Collaborate session or play a Collaborate recording, you will have to download and install the Launcher. Please allow sufficient time before the session to do so, or you can download & install ahead of time using the appropriate link below.
Direct links to download Collaborate Launcher:
for Mac (58Mb) = https://na-downloads.elluminate.com/bcl/BlackboardCollaborateLauncher
for Windows (40Mb) = https://na-downloads.elluminate.com/bcl/win/BlackboardCollaborateLauncher
If you have installed the Collaborate Launcher and it's still not working, please see I can't get my Collaborate Session or Recording to open