If "Reset View" doesn't help, check waveform luminosity slider.

- reset.png (943.38 KiB) Viewed 1576 times
If that doesn't help, go to Workspace->Videoscopes->Videoscopes On. Turn them on and then close them.

- workspace.png (339.99 KiB) Viewed 1576 times
If you are working with two monitors, try to detach them and move them to other monitor.
If that doesn't help, try reseting UI. Workspace->Reset UI Layout.
Also try if they work creating new project, new timeline new files...