(please quote your code)
It seems that you are passing args to the build process in using environment variables. Please make sure that you have done everything described here:
https://juliadocs.github.io/Documenter.jl/dev/man/hosting/
You may also want to pin to a specific version of Documenter in the relevant Project.toml, to make sure things don’t break if the interface changes.
Also, I like to look at the build setup of Documenter.jl itself to figure out the recommended way of doing things: