Hello Maresagc99
I can understand how that can be annoying if you are not able to play songs, especially if you have already purchased them. Let's see if we can get those back to playing on your iPod touch.
The first thing I would tell you to do is to delete those songs off your iPod touch. You can do that by swiping to the left on each song and tap delete.
Delete music, movies, podcasts, and other content from your iPhone, iPad, iPod touch
https://support.apple.com/en-us/HT204343
Once you have deleted the songs that are giving you issues, you can then navigate to the iTunes Store app and download them again. I have quoted the steps below to get you what you need.
Download past purchases from iTunes
https://support.apple.com/en-us/HT201272
On an iPhone or iPod touch
- Open the iTunes Store app.
- From the menu the bottom of the screen, tap More.
- Tap Purchased, then tap Music.
- Tap Not on This iPhone or Not on This iPod.
- Scroll to find the song that you want to download, then tap it.
- Tap the Download icon to the right of the title. Your song downloads to your device.
Have a great day