Game Window goes black on play in editor

My class is working in Unity version 2021.3.5f1 which is required for the SDK that we are using. This happens every time whether or not we are using Mac OS or Windows. Whenever we click the play button in the editor to test our level, we get a totally black screen. We would expect something like “Display 1 No Camera Rendering” but the screen is just black and we do have a camera set up in the scene. It also takes a long time to try and reload the the script assembles. By the time we get to click on the Scene view, the animation that we are checking has already played out.
I have tested this with using just a floor on which sits a cube with an animation (but haven’t applied the script to play the animation because it also does not work in this version .It does in every other Unity version I have tried. The animation is supposed to be triggered by a capsule when it touches the floor. So , there are not scripts applied. The students have more elaborate setups but it is impossible to test out as the game window just goes black.It is not the Play mode tint.

In theConsole we get the following message:
ArgumentOutOfRangeException: Index was out of range. Must be non-negative and less than the size of the collection.
Parameter name: index