What model & year are your Lyriks – do they definately have buttercups already?
If they do, then the 150mm air shaft that you bought probably isn’t the one for your forks – it will be for the previous versions.
Air shaft upgrades: –
2021 C1 Lyriks – Debonair (no buttercups)
2023 D1 Lyriks – Debonair + (with buttercups)
I have just added a 160mm air shaft upgrade to my 2023 Lyrik Select+.
The fork doesn’t have buttercups as standard (2023 Lyrik Ultimate does) but the correct upgrade shaft does have buttercups.
So OK to run buttercups in just one side, but you may have an older fork & upgrade kit that is not compatible with buttercups?