Let me add last comment to this question because now all things sorted out.
Overall as per my understanding because of heating issue my NMVe SSD stopped working because I have plugged SSD within motherboard through cheap market adapter without any kind of thermal paste.
After removing from iMac, I have tested NVMe SSD with enclosure to other computers but it didn't work so I have to request for the replacement and I did it successfully and I got the new piece from the company.
Now I am using it with enclosure for my regular usage and its working great though enclosure is heating too much at the time of heavy load.