Hello hegelok1,
Welcome to Apple Support Communities!
If we understand your post correctly, you're getting a message saying that the track you're trying to add in Memories is not supported. We'd like to help!
This can happen due to copyrights. You can still choose to share the memory but it will have to be with a non-copyrighted music that you will be prompted to choose.
The article below will help with adding Memories.
Use Memories in Photos on your iPhone, iPad, or iPod touch
Let us know if you have any questions.
Thank you for using Apple Support Communities.
Take care!