Something is corrupt in your animated GIF file. A gif file is not a video file. When you drop an animated gif file onto Photoshop. Photoshop should open it as a layered document with a frame animation Time Line Panel.
Dropping an Animated Gif onto a Project open in Photoshop should Place in the animated gif as a Smart Object Layer
.
It will be like a Frame Capture it will not animate.
You can create a frame animation in your project and open the animated gif in photoshop and copy and paste frames between documents.
JJMack