Double clicking on a new Lazarus .lpi file, does open the code and form. As noted it wasn’t working on older .lpi projects.
Something strange is happening though. After getting things working, I’m unaware of making any other changes. But perhaps look at another project…once again not making any changes or saving that I’m aware of. When I go back to previously saved working project…it no longer works! Thank God after the project worked, I closed it then tar gziped it, Delete now not working project…extract working project…and it works again!
So I don’t think File/Close All is trustworthy. I’m guessing it’s probably OK to do that. But then you should totally exit/restart Lazarus before doing further work on a project.