It seems that for a fresh install on the latest LTS, a restart is required for blueocean to be able to open pipelines (this is a minor regression).

Steps to reproduce:

• Launch a 2.7.3 instance with a fresh jenkins_home
• Install "recommended plugins"
• Create an admin user (as recommended)
• Create a standard pipeline (dont' run it yet)
• Install blue ocean from plugin manager
• Press "try blue ocean" - it will render
• Try to open the pipeline in blueocean - it will be 404

If you try to access the rest api, it all seems to be 404'ing, like the route isn't available at all?

Restarting it and things work fine.

this only matters as it may be a first impression issue.