If all your MP3-files fail to import then you’re probably running Windows N without media codecs. You can download the missing media support from Microsoft:
Thanks for your suggestion. I tried that but the option is not available or is already installed. Windows Media Player Legacy is installed.
Here is a summary of my setup:
Windows 11 Pro, 10.0.22621
Dell XPS 8950, x64-based PC
i7-12700, 2100Mhz, 12 cores
Bios date 03/09/23