Hello,
Is this a Kaltura CE install, OnPrem or our SaaS?
If OnPrem or SaaS, please open a ticket with the support team.
If CE, does it a simple embed play the video? you can get a embed code by going to KMC->Content->entry row->preview and embed, where you will see a tiny URL link to the video embed.
If it does not play there, then the issue has nothing to do with Blackboard and you can provide this tiny URL here so I can look into it, if it does work with a standalone embed, then in Blackboard, which I imagine is not publicly accessible, I suggest you open your browser's devtools, try to play the video and look for errors in both the "Network" and "Console" tabs, you can then start by pasting the errors here and I'll do my best to assist you further.
Also, in the case of CE, we will probably need someone who has SSH access to the Kaltura server so we can look at the logs.