Sometimes there is a possibility even after assigning the Detail Styles, one will not able to see the 2D views in the Views tab. To avoid this issue please follow the steps below.
1. Open the 2D Detail Center. 2. In the Detail center dialogue box, under Parts tab, click on the settings. 3. This will open the settings dialogue and, in this dialogue, check the option ‘Take over into view list’ . 4. This will allow the entry of element into views tab after assigning the Detail Style as you can see in the image below. In this way, this issue can be resolved.