Sorry to not offer immediate help, but your post is somewhat confusing.

It sounds like you’re running a Mac, using S2 to connect to your IKEA speakers. Where is your music stored? It can’t be in the router, it has to be either on an NAS or the hard drive of your Mac. Does streaming from a TuneIn radio station work?

And I also infer, perhaps incorrectly, that sometimes your system connects to the IKEA speakers, sometimes it doesn’t?

You seem to be posting about two different issues. First, an inability to find your music files, wherever they’re stored, and second, an issue with S2 being unable to find your speakers. Am I correct? Can you provide more information about how these IKEA speakers are connected to your router, what OS is on your Mac?

@Airgetlam Sorry for not replying sooner and the misunderstanding.

Yes, I am using a Mac Mini running macOS Ventura 4.1. S2 is able to connect to the speakers, however it tells me that my music files couldn’t be found. My music files are stored on an NAS. Streaming from iHeart Radio and Spotify works perfectly fine.

I hope I answered your question.

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HelpingIsKind

Ok, that data really helps. 

Sonos S2 uses SMB v2 or SMB v3 to reach out to up your NAS to get the music data. Which NAS are you running, and is one of those two versions of SMB turned on, or are you still running SMB v1? Or do you know how to tell?
 

Have you tried to submit a system diagnostic within 10 minutes of experiencing this problem, and call Sonos Support to discuss it? There would likely be some pretty good data that the Sonos folks could use to help you connect to your music library. And you’ve followed all the instructions here, correct? 

The fact that your speakers can play iHeart Radio and Spotify means that they’re set up correctly, it’s just the NAS situation we need to resolve.