Happens to all of us. Julia’s builtin Pkg does throw an error informing us that our added registries have no such name, even gives some good suggestions:
(@v1.11) pkg> add FowardDiff
Updating registry at `C:\Users\Benny\.julia\registries\General.toml`
ERROR: The following package names could not be resolved:
* FowardDiff (not found in project, manifest or registry)
Suggestions: ForwardDiff ForwardDiff2 Fourdfp FiniteDiff CamiDiff ForwardDiffPullbacks PolyesterForwardDiff
But Pluto’s own error message obscures that and gives the other possible reasons and suggestions instead.