2550nex, installed generic backup camera 6 months or more ago.  Worked perfectly until last week.  Now it won't go into backup mode in reverse, it stays on the Waze screen, which is my default screen.  When I'm backing up it still senses distance because the beeping works.  I was able to force it on but I don't get a view, just a black screen saying it could be in reverse.  Nothing has changed.  All my fuses are good.  Was trying to avoid pulling it out as it's a very tight fit in my dash.  On the settings screen I only get three options, view grid, camera polarity and camera off/on.  No view camera.  I was able to force it by touching the a/v button option.  Camera has power at the hatch connection.