The extension link you gave no longer exists.
The old “defeated” RBS cipher was withdrawn in 2016. That was NINE YEARS ago.
Recently SketchUp upgraded to Ruby 3.x, which introduced their own type definition files that also use the RBS filetype. This created a clash between the two file types. This happened outside SketchUp’s authority, and nothing can be done to prevent the clash.
It is just time to move on, and extension developers should have long since switched over to using RBE instead of RBS. Your only recourse is to ask the developer of that extension to redeploy it using RBE.