Some system specs in your signature would help. What platform are you running? What version of Studio One are you running? Are you in console view or arrange view when you say Mute/Solo buttons are not working?

Mute/Solo functions should all be working. Have you got a master mute/solo function engaged.

Yes, sorry...forgot. I'm running Windows 10 Home 64bit. My S1 version is 4.6.1.559.
I had everything running fine on my other computer Same specs as above and all was fine. But it died.
So I have a new computer now and have finally got everything set back up. The only anomaly I know of is the Solo/mute thing.
I work mainly in console view.
If I'm playing a song and I click the solo button on a track, that track and a few others will play normally with every other track lower volume but not much lower.
The mute button on any track doesn't seem to work at all.

When you say "master mute/solo" you're talking the global solo/mute right? They are off. The Main mute/solo is off too.

Strange. I've been playing with this issue off and on since yesterday. I've opened the song several times with the same solo anomaly.
About 40 minutes ago, I made a small change and saved/exited. Came back about 30 minutes later and opened S1 and my song. It's working normally now. I closed S1 and reopened everything and still working normally. Mute working normally too.
I guess it is fixed? I'll keep an eye on it. Maybe it had something to do with the fact I had to move the song/folders etc from the other pc/drive? I'm not positive but I don't know if I save it before this happened or not. I don't think I did.
Not sure, but hope it keeps on keeping on.

Additional info. The solo/mute buttons work fine over the speakers. It's while using the headphones is where it doesn't solo/mute. The headphones are working normally other than this. Is there a setting that I need to throw?

In Song Setup, in the Outputs, I've added another channel for headphones (Phones 7 and 8 selected with L and R). Main L and Main R are not enabled. Cue Mix is checked.
Thanks

Thats normal. Cue Mix Outputs are sent prior to Solo/Mute functions in the signal flow. Normally that is. However this can be changed. Go to Settings/(Preferences)/Advanced/Console. Look right down the bottom. See Cue Mix Follows Channel. Check this and then Cue mixes will follow Mute/Solo settings.

That's it! Fixed it.
I've got to remember this one.
Thank you so much!

Good to hear!