Failure: PlotlyJS does not compile because of WebIO

Running julia 1.6.2 on MacOS Monterey.
in a new project, following Part 3. Basic Callbacks | Dash for Julia Documentation | Plotly

pkg>add Dash DataFrames PlotlyJS UrlDownload

pkg>build PlotlyJS

fails
ERROR: LoadError: HTTP/2 404 while requesting https://pkg.julialang.org/binary/WebIO.jl/v0.8.90/webio.bundle.js
Stacktrace:
[1] (::Downloads.var"#3#4"{Nothing, Vector{Pair{String, String}}, Float64, Pkg.PlatformEngines.var"#14#16", Bool, Nothing, String})(output::IOStream)
@ Downloads /Users/julia/buildbot/worker/package_macos64/build/usr/share/julia/stdlib/v1.6/Downloads/src/Downloads.jl:233
[2] open(f::Downloads.var"#3#4"{Nothing, Vector{Pair{String, String}}, Float64, Pkg.PlatformEngines.var"#14#16", Bool, Nothing, String}, args::String; kwargs::Base.Iterators.Pairs{Symbol, Bool, Tuple{Symbol}, NamedTuple{(:write,), Tuple{Bool}}})
@ Base ./io.jl:330
[3] arg_write(f::Function, arg::String)
@ ArgTools /Users/julia/buildbot/worker/package_macos64/build/usr/share/julia/stdlib/v1.6/ArgTools/src/ArgTools.jl:86
[4] #download#2
@ /Users/julia/buildbot/worker/package_macos64/build/usr/share/julia/stdlib/v1.6/Downloads/src/Downloads.jl:221 [inlined]
[5] download(url::String, dest::String; verbose::Bool, headers::Vector{Pair{String, String}}, auth_header::Nothing, io::IOContext{IOStream})
@ Pkg.PlatformEngines /Users/julia/buildbot/worker/package_macos64/build/usr/share/julia/stdlib/v1.6/Pkg/src/PlatformEngines.jl:270
[6] download(url::String, dest::String)
@ Pkg.PlatformEngines /Users/julia/buildbot/worker/package_macos64/build/usr/share/julia/stdlib/v1.6/Pkg/src/PlatformEngines.jl:247
[7] download_bundle(name::String, path::String, url::String)
@ Main ~/.julia/packages/WebIO/cOHMI/deps/bundlepaths.jl:39
[8] download_js_bundles()
@ Main ~/.julia/packages/WebIO/cOHMI/deps/bundlepaths.jl:52
[9] top-level scope
@ ~/.julia/packages/WebIO/cOHMI/deps/build.jl:15
[10] include(fname::String)
@ Base.MainInclude ./client.jl:444
[11] top-level scope
@ none:5
in expression starting at /Users/alun/.julia/packages/WebIO/cOHMI/deps/build.jl:15

Trying to build WebIO separately gives the same error.
pkg>status
[1b08a953] Dash v1.1.0
[a93c6f00] DataFrames v1.2.2
[f0f68f2c] PlotlyJS v0.18.8
[856ac37a] UrlDownload v1.0.0

Anyone know a way around this?
thanks