Is 'astroPricingTravel' the name of the package you're building?
I don't see an error message in the image posted, but it's difficult to read. For subsequent error messages, please post them as text. The preformatted text markup will keep it monospaced.
What is the problem with the highlighted step? I think that step is creating a temporary directory, copying the package files there, and attempting to install the package into the from there.
If you're using plumber for a simple task, calling plumb on the r file might be sufficient. Are you building a package to better manage the collection of functions?