This article applies only to students who are using Canvas as their LMS.
If you are trying to access a recording and are encountering a message saying, "This assignment was locked", it means the assignment has passed its availability window and is no longer available.
If you are trying to access the Playback Room to view a prior assignment's recording, what you can do is click on a different assignment link (e.g. the link for the current week) and navigate to the Playback Room from there. Once inside the Playback Room, you should be able to access all available recorded sessions.
Below is an example screenshot of the "This assignment was locked" message in Canvas: