Hard to tell from this. Is there any warning or error in the log (check the Console: Shift + F10). What type of texture is that?
This is my first time rendering with arnold. So i am a noob in this render engine.hope this will clear the confusion.
Ok, so Arnold utilizes tx textures to optimize render time and memory usage. By default it generates tx files next to the original images. The error in the log says, that tx generation failed because you don't have write permission in the Program Files folder.
I'm not sure if this is causing trouble for GPU though, it should not. You can try to turn off auto tx generation in Render Settings > Main > Textures to see if that solves the problem.
Or you can move the HDRI Browser plugin to the app data folder, e.g c:\Users\[myuser]\AppData\Roaming\MAXON\Cinema 4D R21_XXXXXXXX\plugins