Cant add .m4p files to itunes library

Apple Music tracks are protected. If you moved from one computer to another while you had an Apple Music subscription and simply signed in you would have seen all of the tracks you expected to see in your library, ready to stream or download, but those you had previously ripped would now be Apple Music tracks. Do you still have the old computer? If not then as you say you will have to rip your CD collection again. See Backup your iTunes for Windows library with SyncToy to secure your library this time.

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Yes, your iPhone can contain a mix of store purchases, personal rips, and subscription content via Apple Music. If you have an active subscription to either Apple Music or iTunes Match then you either sync your device to your iTunes Library or have it connect to your iCloud Music Library. If you have an iCloud Music Library any content you add to the library from one computer becomes added to the iCloud Music Library and then available at any other computer or device. Crucially if the mechanism is Apple Music then the new copies on other device and computers, or the original if you remove downloads or have some kind of crash, will be DRM copies. With iTunes Match they will normally be 256k DRM-free AAC copies. Backing up your original local copies of anything you rip is necessary to make sure you can always go back to them if needed.

I suspect the method you used (or perhaps didn't use) to move from one computer to the other caused the problem. I would normally recommend using SyncToy for both the final backup on the old computer and then an initial restore into a new computer, as you are then set up for maintaining the backup going forward.

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Do you have an active subscription to Apple Music?

Did you have one previously?

Have you moved computers from the one that the tracks were originally ripped on?

Do you have a backup of your library and media?

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