Diagnostics does not recognize my iPOD NANO. What do I do now ? Will not sync.

Diagnostics does not recognize my iPOD is connected.

Does the iPod appear in iTunes (as a device button on the horizontal bar) when you connect it? Here's a screenshot of my iTunes window (upper left corner) with an iPod connected. The iPod's device button is circled in red.

Regardless of what "diagnostics" says, is the iPod's device button shown in iTunes window when you connect the iPod?

OK, that's good; iTunes sees your iPod. Your iPod may be set to Manually manage music and videos. This is the default setting, if this iPod is new, or you are using a new/different iTunes library (or you just "restored" the iPod).

If you want to use automatic syncing for music, you need to set it to Sync Music. Select the iPod in iTunes (click its device button on horizontal bar) to show its settings screen in iTunes window. Along the left side (in the sidebar), under Settings, click Music. To the right, the iPod's Music settings screen is shown.

NOTE: Any songs on the iPod that are not in your iTunes library will be lost.

Checkmark the box for Sync Music. This turns ON automatic syncing. If your iTunes music library can fit on the iPod, you can choose the option to sync Entire music library. Otherwise, choose the option to sync Selected playlists, artists, albums, and genres; then make your selections from the lists below. For example, you can create and maintain (one or more) playlists in your iTunes library with songs you want on the iPod. Back on the iPod's Music settings screen, under Playlists, select (checkmark) those playlists.

Click Apply to sync your music library (or selected portion of it) to the iPod. Going forward, iTunes automatically keeps your iPod "in sync" with changes to your music library (or selected portion of it), when you connect the iPod (or click Sync if already connected).

If this is not the reason for the iPod not syncing, please post back with any additional details.

Do you subscribe to iTunes Match or Apple Music? If you do, that gives you an iCloud Music Library. OR are the songs that do NOT sync all purchased from the iTunes Store? If so, that could mean you are accessing your songs from Apple's servers ("iCloud"). The songs still appear in your iTunes library, and play (by streaming), but they will not sync to your iPod unless the song files are stored locally on your computer's drive.

this Nano is 5-6 years old and has synced perfectly all along -UNTIL I GOT A NEW COMPUTER.

Since you got a new computer recently, perhaps those "52" songs are the ones you added after getting the new computer. So they are all stored locally on the computer's drive. The rest are currently being accessed from iCloud.

You can check by doing a right-click Get Info (in iTunes) on one of the songs that does not sync. On the Info window, go to the File tab and look at location. Does it show a file path to where the song file is stored on your computer's drive, or does it say iCloud?

Are they all songs purchased from the iTunes Store, or do you have an iCloud Music Library from a paid subscription to either Apple Music or iTunes Match.

As a service for customers who buy songs (and other media) from the iTunes Store, Apple makes purchased items available for streaming from iCloud. So, if you own an iPhone or iPad (or a secondary computer), you can play (stream) your purchased songs on those devices by associating them with your Apple ID. You don't need to download the song files on each device. Additionally, if you pay for a subscription to iTunes Match or Apple Music, you get an iCloud Music Library; then all of your songs become accessible from iCloud (not just the ones you purchased from iTunes Store).

To make them sync to your iPod, you need to download the songs to your computer's drive. To do this with one action (instead of one song at a time), show your music library in iTunes. Use the Songs view (with control at right end of horizontal bar) to show your library as a plain song list with columns. Click any song on the list to highlight it, then Edit -> Select All from the menu bar OR Control-A on keyboard (Command-A for a Mac). This selects all of your songs at the same time. Right-click selection and Download. iTunes should begin downloading all songs that are being accessed from iCloud. This may take a while. You can track progress in the iCloud Download column of song list. This column is narrow with a cloud symbol in the heading. If you don't see this column on your song list, right-click on the heading row to show/hide columns.

After downloading completes, try syncing your iPod again.

NOTE: IF you happen to have a subscription to Apple Music, some of your songs may still not sync to your iPod after downloading. Please post back.