You will need to delete everything from the library and re-add them to your library.
Please follow these instructions.
1. Open RealPlayer.
2. Go to Music under Library tab
3. Choose "All Music"
4. Select all files and hit Delete button
5. Hit Delete button.
Note: DO NOT Check the box that says "Also delete files from hard drive". If you check this, you will lose all files from your hard drive.
6. Once everthing has been removed from your RP Library, you can re-add them to your library.
Instructions to re-add are here: https://customer.real.com/hc/en-us/articles/205035417-Scan-disk-for-media