Problem with collision detection

I am on my fourth Unity project. In the first three, I used RigidBody onCollision type detection, as well as onTrigger for certain objects in the environment. With the fourth project, the scripts no longer receive the onTrigger or onCollision events. I can push objects around with the player but the events don't trigger.

Thinking I had made some mistake, I started a brand new project and added a capsule and a cube. Each with isTrigger on a capsule and box collider respectively. There is a terrain which is completely flat. The cube runs into the capsule collider. No events. Such to rigidbody on cube and none on capsule. No event. Put rigidbodies on both. No events. The scripts have onTrigger and onCollision enter event handlers that print the name of the other object. When I check the previous projects, they work fine.

I have no idea what I could have done to disable event detection. The projects have an EventSystem object that is active but it is not sending any messages. What should I check? Where should I look?

Thanks for any input!