Recently, we encountered an issue with Dynamics 365 where the Activity Dropdown no longer displays options for activities when attempting to add them directly to the related record. It would display a message stating "No Options Available" or it would stay stuck "Loading" like in the below screenshot.
This happened due to a feature update in the 2022 Wave 2 update from Microsoft for Dynamics 365. This new feature now gives you the ability to pick what activities you want to show on these drop downs so it is not cluttered with unnecessary options that are never used. This feature can be disabled completely by going into the Power Platform Admin center then into the organization's settings. From here, click "Features" and scroll down to the "Activities" section where you will see the following option. If you disable the setting in the screenshot below, all activities will show in the drop down that were previously there.
If you would like to use this feature and customize the activities that show in the drop down, you can do this through customizations. From Dynamics 365 Advanced Settings, go into customizations then choose the option to "Customize the System." From here, select "Model-Driven Apps" then select the app you would like to customize with only select activity entities.
From the App Designer, click on "Entities" under components on the right.
From here, you can add the activity entities to the app you are modifying. Once you have added all the activity entities you want to show in the (