Azure pipeline YAML – install project nuget packages

I have a solution containing roughly 100 aps.net projects, one of which is a Selenium test suite. I wish to create an Azure pipeline that installs only the Nuget packages of the Selenium project, and then builds and runs the Selenium tests. When running the VSBUILD step, my pipeline fails, claiming that the project NuGet packages are missing, so seemingly I’m not getting the project packages correctly. I have the following YAML: