I have created a turntable animation by rotating camera around the 3d model. but when I try to export this animation it does not export animation in .glb format, rather it just export a simple 3D model. Please help me with this, I have spent almost a whole day on this but could not succeed. Thanks in advance.
Rotate the object, not the camera. Camera movement is not exporting to desired format only animation of models.
I do think Blender exports camera animation to glTF. But you might need a specialized viewer to display that camera’s view (example feature request: https://github.com/google/model-viewer/issues/2063). Most are probably going to ignore the camera and just display the scene. Rotating the model (as @Andreal suggests) would work.