I have removed all the files from my Lumia 640 XL and now my playlist shows a red exclamation mark for those missing files. Can someone assist me with resetting/rebuilding my Groove Music file list, just like it is when I start my mobile for the first time where it builds the playlist?
Unfortunately Microsoft removed the ability to reset Groove Music from the Settings menu. However, you can delete everything in the Grove Music database and start over from scratch.
NOTE: These instructions assume all of your music is being stored on a microSD card. If this isn't the case you should buy a microSD (they're dirt cheap anymore, so you have no excuse) and transfer your music to it before proceeding.
Power off your phone and remove the microSD card that contains your music library.
Power up the phone, launch Groove Music, and select the "Albums" view.
Press and hold the topmost album, and when the menu pops up, select it.
Once the album is selected, tap the Menu (the three dots in the lower right corner) and "Select All" albums. BE PATIENT! Depending on how many albums you have it can take five to ten minutes for Groove Music to select all of them!
Tap the trash can to delete all of the selected albums. Again, BE PATIENT! because it will take time for Groove Music to delete all of the albums.
Once all of the albums are deleted, power off your phone, reinsert the microSD card, power the phone back up, select Groove Music, and it will start reloading your music collection into the database.