What version Premiere Elements, what computer operating system?
Where are these files coming from? Are these iTunes music files? If so, then the classical way to resolve that type of problem is to convert the music to WAV version.
Conversion can be done in iTunes iTunes: How to convert a song to a different file format - Apple Support
Alternatively, you can do this conversion in the free Audacity, but the iTunes way works nicely.
Please consider, give more details, and then we will decide what next based on the details in your reply.
Thank you for the answer! It is very useful.
I will ask with more detail in the future.
Thanks for the follow up, and good to learn that the information in the thread was helpful.
Please do not hesitate to ask questions and to ask for clarification on your Premiere Elements workflows.
Best wishes with your Premiere Elements projects.