Please update to the latest stable (5.1.0) as the 5.0.0 series is no longer supported.
Then, please copy the full version information from About KiCad -> Copy Version Info.
Are you launching Pcbnew standalone or from the KiCad manager (in a project)?
Since it used to work and now it doesn't suggests there was a change on your machine that caused this.
Please update to the latest stable (5.1.0) as the 5.0.0 series is no longer supported.
Then, please copy the full version information from About KiCad -> Copy Version Info.
Are you launching Pcbnew standalone or from the KiCad manager (in a project)?
Since it used to work and now it doesn't suggests there was a change on your machine that caused this.