I've often run a stereo miniplug out to two RCA plugs into a stereo amp for an iPod, boombox, laptop, without problems. My main system runs that way, with a miniplug into the headphone out on a Win10 machine, into a decent stereo amp and floor speakers. I have another system running the USB out into an M-Audio interface, then RCA cables into that stereo. Both work great..

I just tried putting speakers on the rec room laptop where the wifi reaches..

Only one speaker works. So here was my troubleshooting order:

swapped the speakers, left for right. Nope, they both work, but only on the one side.

Swapped the stereo amp for a different one. Same results.

Okay, maybe it's the laptop port. Put in earbuds from my phone, both sides work.

Aha! It's the cable. Got two more miniplug to RCA cables, still only one side audio. Not the cable, unless I have 3 bad ones.

Then and only then went to google: common problem, adjust the speaker volume and balance settings and it goes away. Nope, still doesn't work.

Still could be the laptop jack. Carry it upstairs to the system known to work. Works fine up there. Great, it's fixed, carry it back down and ................ nope, won't work on the amp down there.

What am I missing? I've tried speakers, amps, cables, and software, I don't know where to go next. Oh, maybe should mention, this is an older laptop.. It came with System 7 but when the harddrive crashed we couldn't get another 7 without paying the cost of another laptop so we put on XP.