I had the same thing and it ended up being a reset. I unplugged the speedo in the back and waited a couple of minutes and plugged it back in. Miraculously, as I have little understanding of what happened, it started working.
David & Sharon with Tar the cat
2007 Holiday Rambler NeptuneXL 36 2002 Jeep Wrangler and 2002 HD Road King Classic Gulfport, MS