why 3d obj file is not opening in photoshop2021

Adobe are updating the core graphics functions in Photoshop. This is driven by the operating systems of Apple and Microsoft in which the old Open GL functions are being removed in the case of Apple, or deprecated in the case of Microsoft. This means that the graphics functions that have worked for years must be rewritten to use Metal and Direct X. At the same time, Adobe are sensibly updating those core functions to deliver the additional speed we require to handle the very large files of today.

Some functionality in Photoshop, such as 3D, still relies on the older Open GL graphics functions. To make these work, an additional preference Preferences>Technology previews>Deactivate Native Canvas has been added to v22.4 and v22.4.1. This can be checked and Photoshop restarted to restore 3D functions to where they were in 22.3

Dave