When I review my Play 5 speaker Pair in the Sonos App and look at the Line-In section, only Line-In (R) is bolded while (L) is greyed. I assume that means only the R channel is getting fed to both speakers?

I’ve made sure the RCA to headphone jack is connected and seated properly in the back of the Play 5.

Any other suggestions, do you have a recommended RCA to Line-in cord?

EDIT: I discovered the highlighted (R) or (L) shows which speaker has the Line-in physically attached, not that only one channel is connected.