Hi SurajitMukherjee-5680!
Does this issue persist all the time?
Can you find the camera device setting in Microsoft Teams?
As TKujala said, we recommend you check if you allow Teams app to access your camera. You can open Windows Settings panel and go to Privacy->Camera. Here you can find a heading saying Allow apps to access your camera.
Besides, if you think that the webcam has no problem, you can also try to restart the app and your computer to see if it can be fixed.
As a supplement, you can refer to: