If you have a course that was developed prior to 2020 it could still contain some Flash content. Browsers no longer support Flash so you will need to convert this content to HTML5 and republish your course in order for these screens to work. Any content in Udutu templates can easily be converted by going into course settings.
If your course contains Flash content that was developed outside the Udutu authoring tool it will need to be recreated and reloaded in your course. This content will not convert automatically like the templates.