Hi @craig.jamieson,
I suggest you start by following this thread and verifying everything is as it should be:
If, afterwards, you still have issues/questions, please post your full config [masking sensitive data] as well as the records from the delivery_profile table and I’ll gladly assist you further.
Also, when making the playmanifest request [made when you hit “play”], please check /opt/kaltura/log/kaltura_prod.log and verify the correct delivery profile was chosen. It may not be what you think it is:)