Error message in adding a package

trying to add pluto package and below is error message i get.

Error: The following package names could not be resolved:

Can you share what you typed?
And the full error message?

The command:

]add Pluto

in the repl works find for me:

(repos) pkg> add Pluto
    Updating registry at `~/.julia/registries/General.toml`
   Resolving package versions...
   Installed RelocatableFolders ─ v0.2.0
   Installed IniFile ──────────── v0.5.1
   Installed MsgPack ──────────── v1.1.0
   Installed ExproniconLite ───── v0.6.13
   Installed FuzzyCompletions ─── v0.5.0
   Installed Configurations ───── v0.17.3
   Installed Pluto ────────────── v0.18.4
    Updating `~/repos/Project.toml`
  [c3e4b0f8] + Pluto v0.18.4
    Updating `~/repos/Manifest.toml`
  [5218b696] + Configurations v0.17.3
  [9a962f9c] + DataAPI v1.9.0
  [e2d170a0] + DataValueInterfaces v1.0.0
  [55351af7] + ExproniconLite v0.6.13
  [fb4132e2] + FuzzyCompletions v0.5.0
  [cd3eb016] + HTTP v0.9.17
  [83e8ac13] + IniFile v0.5.1
  [82899510] + IteratorInterfaceExtensions v1.0.0
  [739be429] + MbedTLS v1.0.3
  [99f44e22] + MsgPack v1.1.0
  [bac558e1] + OrderedCollections v1.4.1
  [c3e4b0f8] + Pluto v0.18.4
  [05181044] + RelocatableFolders v0.2.0
  [6c6a2e73] + Scratch v1.1.0
  [3783bdb8] + TableTraits v1.0.1
  [bd369af6] + Tables v1.7.0
  [5c2747f8] + URIs v1.3.0
  [0dad84c5] + ArgTools
  [56f22d72] + Artifacts
  [2a0f44e3] + Base64
  [ade2ca70] + Dates
  [8ba89e20] + Distributed
  [f43a241f] + Downloads
  [7b1f6079] + FileWatching
  [b77e0a4c] + InteractiveUtils
  [b27032c2] + LibCURL
  [76f85450] + LibGit2
  [8f399da3] + Libdl
  [37e2e46d] + LinearAlgebra
  [56ddb016] + Logging
  [d6f4376e] + Markdown
  [ca575930] + NetworkOptions
  [44cfe95a] + Pkg
  [de0858da] + Printf
  [3fa0cd96] + REPL
  [9a3f8284] + Random
  [ea8e919c] + SHA
  [9e88b42a] + Serialization
  [6462fe0b] + Sockets
  [fa267f1f] + TOML
  [a4e569a6] + Tar
  [8dfed614] + Test
  [cf7118a7] + UUIDs
  [4ec0a83e] + Unicode
  [e66e0078] + CompilerSupportLibraries_jll
  [deac9b47] + LibCURL_jll
  [29816b5a] + LibSSH2_jll
  [c8ffd9c3] + MbedTLS_jll
  [14a3606d] + MozillaCACerts_jll
  [4536629a] + OpenBLAS_jll
  [83775a58] + Zlib_jll
  [8e850b90] + libblastrampoline_jll
  [8e850ede] + nghttp2_jll
  [3f19e933] + p7zip_jll
Precompiling project...
  11 dependencies successfully precompiled in 11 seconds (12 already precompiled)

(repos) pkg> 

What I typed was

]add Pluto

Or is Julia case sensitivity??

Julia is case-sensitive but your command looks fine. Maybe you could share a screenshot of your console?

I’ve also tried it Julia 1.7.2.

]

add Pluto

It then does a lot of positive things, but then errors right at the end:

ERROR: Error when installing package Pluto:
IOError: rm("C:\\Users\\fking\\AppData\\Local\\Temp\\fU2Iy2zbtVHB\\frontend\\components"): directory not empty (ENOTEMPTY)
Stacktrace:
 [1] uv_error
   @ .\libuv.jl:97 [inlined]
 [2] rm(path::String; force::Bool, recursive::Bool)
   @ Base.Filesystem .\file.jl:299
 [3] rm(path::String; force::Bool, recursive::Bool) (repeats 2 times)
   @ Base.Filesystem .\file.jl:287
 [4] rename(src::String, dst::String; force::Bool)
   @ Base.Filesystem .\file.jl:968
 [5] rename
   @ .\file.jl:964 [inlined]
 [6] #mv#17
   @ .\file.jl:412 [inlined]
 [7] install_archive(urls::Vector{Pair{String, Bool}}, hash::Base.SHA1, version_path::String; io::Base.TTY)
   @ Pkg.Operations C:\Users\fking\AppData\Local\Programs\Julia-1.7.2\share\julia\stdlib\v1.7\Pkg\src\Operations.jl:522
 [8] macro expansion
   @ C:\Users\fking\AppData\Local\Programs\Julia-1.7.2\share\julia\stdlib\v1.7\Pkg\src\Operations.jl:698 [inlined]
 [9] (::Pkg.Operations.var"#45#50"{Bool, Pkg.Types.Context, Channel{Any}, Channel{NamedTuple{(:pkg, :urls, :path), Tuple{Pkg.Types.PackageEntry, Set{String}, String}}}})()
   @ Pkg.Operations .\task.jl:423

Pluto is therefore not installed. The folder is empty now, though.

Looks like a bug to me. It says it’s trying to delete some folder in a temporary directory but errors because the folder isn’t empty. My guess is that something messed up your environment.
I would guess that it’s probably fine to delete this directory on your own and try again (it says it is a temp folder after all).
But first I would maybe try installing in a fresh environment:

] activate temp
add Pluto

If that works you should maybe consider cleaning up your main environment. Hope that helps