While talking to the managers about the training program, you’ve realized that they have other engagements, and they cannot attend any training before November 2021.
In this scenario, we have an event for the availability of the managers. Go to the Training deliverable and click on the Add Event button. Then open the newly created event, rename it to Managers availability for training, and set its Earliest Start to 2021-11 (or a different date that matches your current date). This is the result:
So far so good. Now open Managers' training, and add Managers availability for training as a predecessor. This is the result:
The Earliest Start field is only available for projects and events because it’s bad practice to apply date constraints directly to deliverables. When you have such constraints, build an event for them, and add the event as the predecessor for the deliverables.