Hi Ritwik,
Sorry for the delayed response.
Please check if downloading new visualizations can help us to narrow down the issue. Refer the link below to download any visualization for Windows Media Player and apply them. Then check if that works in "Now Playing Mode." If it plays fine, the visualization pattern or theme may have been corrupt.
https://support.microsoft.com/en-us/help/17878/visualizations-for-windows-media-player
Please let us know the status so that we can assist you further.