You probably have too many packages loaded into your current environment. My v1.9 environment is almost completely empty. You should probably just created a special environment just for Pluto. There is very little reason to have any other package in the same environment since each notebook creates it’s own environment anyways.
Below I demonstrate how to create a global shared environment called “plutoenv”. You can access this from any directory by activating @plutoenv.
using Pkg
Pkg.activate("plutoenv"; shared = true)
Pkg.add("Pluto")
using Pluto
Pluto.run()
Alternatively,
using Pkg
pkg"activate @plutoenv"
pkg"add Pluto"
using Pluto
Pluto.run()